Bitcoin v0.1 release discussions from Cryptography mailing list
2009 Jan 25
See all posts
Bitcoin v0.1 release discussions from Cryptography mailing list @ Satoshi Nakamoto
- Author
-
Satoshi Nakamoto
- Email
-
satoshinakamotonetwork@proton.me
- Site
-
https://satoshinakamoto.network
I have put the Bitcoin v0.1 release announcement on the Cryptography
mailing list about 3 weeks ago, here are some discussions from Hal
Finney, Jonathan Thornburg, etc.
Bitcoin v0.1
released, 2009-01-08 19:27:40 UTC
Announcing the first release of Bitcoin, a new electronic cash system
that uses a peer-to-peer network to prevent double-spending. It's
completely decentralized with no server or central authority.
Here are 3 screenshots of the client's UI.
Download link:
https://downloads.sourceforge.net/bitcoin/bitcoin-0.1.0.rar
Windows only for now. Open source C++ code is included.
- Unpack the files into a directory
- Run BITCOIN.EXE
- It automatically connects to other nodes
If you can keep a node running that accepts incoming connections,
you'll really be helping the network a lot. Port 8333 on your firewall
needs to be open to receive incoming connections.
The software is still alpha and experimental. There's no guarantee
the system's state won't have to be restarted at some point if it
becomes necessary, although I've done everything I can to build in
extensibility and versioning.
You can get coins by getting someone to send you some, or turn on
Options->Generate Coins to run a node and generate blocks. I made the
proof-of-work difficulty ridiculously easy to start with, so for a
little while in the beginning a typical PC will be able to generate
coins in just a few hours. It'll get a lot harder when competition makes
the automatic adjustment drive up the difficulty. Generated coins must
wait 120 blocks to mature before they can be spent.
There are two ways to send money. If the recipient is online, you can
enter their IP address and it will connect, get a new public key and
send the transaction with comments. If the recipient is not online, it
is possible to send to their Bitcoin address, which is a hash of their
public key that they give you. They'll receive the transaction the next
time they connect and get the block it's in. This method has the
disadvantage that no comment information is sent, and a bit of privacy
may be lost if the address is used multiple times, but it is a useful
alternative if both users can't be online at the same time or the
recipient can't receive incoming connections.
Total circulation will be 21,000,000 coins. It'll be distributed to
network nodes when they make blocks, with the amount cut in half every 4
years.
first 4 years: 10,500,000 coins
next 4 years: 5,250,000 coins
next 4 years: 2,625,000 coins
next 4 years: 1,312,500 coins
etc...
When that runs out, the system can support transaction fees if
needed. It's based on open market competition, and there will probably
always be nodes willing to process transactions for free.
Satoshi Nakamoto
From: Hal Finney,
2009-1-11, 02:22:01 UTC
Satoshi Nakamoto writes:
Announcing the first release of Bitcoin, a new electronic cash system
that uses a peer-to-peer network to prevent double-spending. It's
completely decentralized with no server or central authority.
Download link: https://downloads.sourceforge.net/bitcoin/bitcoin-0.1.0.rar
Congratulations to Satoshi on this first alpha release. I am looking
forward to trying it out.
Total circulation will be 21,000,000 coins. It'll be distributed to
network nodes when they make blocks, with the amount cut in half every 4
years.
first 4 years: 10,500,000 coins
next 4 years: 5,250,000 coins
next 4 years: 2,625,000 coins
next 4 years: 1,312,500 coins
etc...
It's interesting that the system can be configured to only allow a
certain maximum number of coins ever to be generated. I guess the idea
is that the amount of work needed to generate a new coin will become
more difficult as time goes on.
One immediate problem with any new currency is how to value it. Even
ignoring the practical problem that virtually no one will accept it at
first, there is still a difficulty in coming up with a reasonable
argument in favor of a particular non-zero value for the coins.
As an amusing thought experiment, imagine that Bitcoin is successful
and becomes the dominant payment system in use throughout the world.
Then the total value of the currency should be equal to the total value
of all the wealth in the world. Current estimates of total worldwide
household wealth that I have found range from $100 trillion to $300
trillion. With 20 million coins, that gives each coin a value of about
$10 million.
So the possibility of generating coins today with a few cents of
compute time may be quite a good bet, with a payoff of something like
100 million to 1! Even if the odds of Bitcoin succeeding to this degree
are slim, are they really 100 million to one against? Something to think
about...
Hal
Reply to
Dustin D. Trammell, 2009-1-16, 16:03:14 UTC
Dustin D. Trammell wrote:
Satoshi Nakamoto wrote:
You know, I think there were a lot more people interested in the
90's, but after more than a decade of failed Trusted Third Party based
systems (Digicash, etc), they see it as a lost cause. I hope they can
make the distinction that this is the first time I know of that we're
trying a non-trust-based system.
Yea, that was the primary feature that caught my eye. The real trick
will be to get people to actually value the BitCoins so that they become
currency.
I would be surprised if 10 years from now we're not using electronic
currency in some way, now that we know a way to do it that won't
inevitably get dumbed down when the trusted third party gets cold
feet.
It could get started in a narrow niche like reward points, donation
tokens, currency for a game or micropayments for adult sites. Initially
it can be used in proof-of-work applications for services that could
almost be free but not quite.
It can already be used for pay-to-send e-mail. The send dialog is
resizeable and you can enter as long of a message as you like. It's sent
directly when it connects. The recipient doubleclicks on the transaction
to see the full message. If someone famous is getting more e-mail than
they can read, but would still like to have a way for fans to contact
them, they could set up Bitcoin and give out the IP address on their
website. "Send X bitcoins to my priority hotline at this IP and I'll
read the message personally."
Subscription sites that need some extra proof-of-work for their free
trial so it doesn't cannibalize subscriptions could charge bitcoins for
the trial.
It might make sense just to get some in case it catches on. If enough
people think the same way, that becomes a self fulfilling prophecy. Once
it gets bootstrapped, there are so many applications if you could
effortlessly pay a few cents to a website as easily as dropping coins in
a vending machine.
Satoshi Nakamoto
https://www.bitcoin.org
From: Jonathan
Thornburg, 2009-1-17, 16:49:45 UTC
On Sat, 17 Jan 2009, Satoshi Nakamoto wrote:
[[various possible uses of Bitcoin et al]]
Once it gets bootstrapped, there are so many applications if you
could effortlessly pay a few cents to a website as easily as dropping
coins in a vending machine.
In the modern world, no major government wants to allow untracable
international financial transactions above some fairly modest size
thresholds. (The usual catch-phrases are things like "laundering drug
money", "tax evasion", and/or "financing terrorist groups".) To this
end, electronic financial transactions are currently monitored by
various governments & their agencies, and any but the smallest of
transactions now come with various ID requirements for the humans on
each end.
But if each machine in a million-node botnet sends 10 cents to a
randomly chosen machine in another botnet on the other side of the
world, you've just moved $100K, in a way that seems very hard to trace.
To me, this means that no major government is likely to allow Bitcoin in
its present form to operate on a large scale.
I also worry about other "domestic" ways nasty people could exploit a
widespread Bitcoin deployment:
- Spammer botnets could burn through pay-per-send email filters
trivially (as usual, the costs would fall on people other than the
botnet herders & spammers).
- If each machine in a botnet sends 1 cent to a herder, that can add
up to a significant amount of money. In other words, Bitcoin would make
botnet herding and the assorted malware industry even more profitable
than it already is.
Is there something obvious I've missed? Is there a clever aspect of
the design which prevents botnets from exploiting the system? Is there a
way for every major government to monitor all Bitcoin transactions to
watch for botnet-to-botnet sending?
– From: "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
– quote by Freire / poster by Oxfam
From: Hal Finney,
2009-1-14 16:48:03 UTC
Jonathan Thornburg writes:
In the modern world, no major government wants to allow untracable
international financial transactions above some fairly modest size
thresholds. (The usual catch-phrases are things like "laundering drug
money", "tax evasion", and/or "financing terrorist groups".) To this
end, electronic financial transactions are currently monitored by
various governments & their agencies, and any but the smallest of
transactions now come with various ID requirements for the humans on
each end.
But if each machine in a million-node botnet sends 10 cents to a
randomly chosen machine in another botnet on the other side of the
world, you've just moved $100K, in a way that seems very hard to trace.
To me, this means that no major government is likely to allow Bitcoin in
its present form to operate on a large scale.
Certainly a valid point, and one which has been widely discussed in
the debates over the years about electronic cash. Bitcoin has a couple
of things going for it: one is that it is distributed, with no single
point of failure, no "mint", no company with officers that can be
subpoenaed and arrested and shut down. It is more like a P2P network,
and as we have seen, despite degrees of at least governmental distaste,
those are still around.
Bitcoin could also conceivably operate in a less anonymous mode, with
transfers being linked to individuals, rather than single-use keys. It
would still be useful to have a large scale, decentralized electronic
payment system.
It also might be possible to refactor and restructure Bitcoin to
separate out the key new idea, a decentralized, global, irreversible
transaction database. Such a functionality might be useful for other
purposes. Once it exists, using it to record monetary transfers would be
a sort of side effect and might be harder to shut down.
I also worry about other "domestic" ways nasty people could exploit a
widespread Bitcoin deployment:
- Spammer botnets could burn through pay-per-send email filters
trivially (as usual, the costs would fall on people other than the
botnet herders & spammers).
- If each machine in a botnet sends 1 cent to a herder, that can add
up to a significant amount of money. In other words, Bitcoin would make
botnet herding and the assorted malware industry even more profitable
than it already is.
It's important to understand that the proof-of-work (POW) aspect of
Bitcoin is primarily oriented around ensuring the soundness of the
historical transaction database. Each Bitcoin data block records a set
of transactions, and includes a hash collision. Subsequent data blocks
have their own transactions, their own collisions, and also chain to all
earlier hashes. The result is that once a block is "buried" under enough
new blocks, it is essentially certain (given the threat model, namely
that attackers cannot muster more than X% of the compute power of
legitimate node operators) that old transactions can't be reversed.
Creating new coins is indeed currently also being done by POW, but I
think that is seen as a temporary expedient, and in fact the current
software phases that out over several years. Hence worries about botnets
being able to manufacture large quantities of POW tokens are only a
temporary concern, in the context of Bitcoin.
There have been a number of discussions in the past about POW tokens
as anti spam measures, given the botnet threat. References are available
from "Proof-of-work system" on Wikipedia. Analyses have yielded mixed
results, depending on the assumptions and system design.
If POW tokens do become useful, and especially if they become money,
machines will no longer sit idle. Users will expect their computers to
be earning them money (assuming the reward is greater than the cost to
operate). A computer whose earnings are being stolen by a botnet will be
more noticeable to its owner than is the case today, hence we might
expect that in that world, users will work harder to maintain their
computers and clean them of botnet infestations.
Countermeasures by botnet operators would include moderating their
take, perhaps only stealing 10% of the productive capacity of invaded
computers, so that their owners would be unlikely to notice. This kind
of thinking quickly degenerates into unreliable speculation, but it
points out the difficulties of analyzing the full ramifications of a
world where POW tokens are valuble.
Hal Finney
From: Bill Frantz,
2009-1-24 23:22:21 UTC
hal at finney.org ("Hal Finney") on Saturday, January 24, 2009
wrote:
Countermeasures by botnet operators would include moderating their
take, perhaps only stealing 10% of the productive capacity of invaded
computers, so that their owners would be unlikely to notice. This kind
of thinking quickly degenerates into unreliable speculation, but it
points out the difficulties of analyzing the full ramifications of a
world where POW tokens are valuble.
Some people tell me that the 0wned machines are among the most secure
on the network because botnet operators work hard to keep others from
compromising "their" machines. I could see the operators moving toward
being legitimate security firms, protecting computers against compromise
in exchange for some of the proof of work (POW) money.
Cheers - Bill
Bill Frantz | When it comes to the world | Periwinkle
(408)356-8506 | around us, is there any choice | 16345 Englewood
Ave
www.pwpconsult.com | but to explore? - Lisa Randall | Los Gatos, CA
95032
From: dan at
geer.org, 2009-1-25 04:07:17 UTC
Bill Frantz writes:
Some people tell me that the 0wned machines are among the most secure
on the network because botnet operators work hard to keep others from
compromising "their" machines. I could see the operators moving toward
being legitimate security firms, protecting computers against compromise
in exchange for some of the proof of work (POW) money.
I'm one of those people. Quoting from my speech of 1/20:
Virus attacks have, of course, become rarer over time, which is to
say that where infectious agents once ruled, today it is parasites.
Parasites have no reason to kill their hosts – on the contrary they want
their hosts to survive well enough to feed the parasite. A parasite will
generally not care to be all that visible, either. The difference
between parasitism and symbiosis can be a close call in some settings,
and of the folks who famously bragged of being able to take the Internet
down in twenty minutes, one has said that a computer may be better
managed once it is in a botnet than before since the bot-master will be
serious about closing the machine up tight against further penetration
and similarly serious about patch management. Therefore, since one can
then say that both the machine's nominal owner and the bot master are
mutually helped, what we see is evolution from parasite to symbiont in
action. According to Margulis and Sagan, "Life did not take over the
globe by combat, but by networking." On this basis and others, bot-nets
are a life form.
Rest of text upon request. Incidentally, I highly recommend
Daniel Suarez's Daemon; trust me as to its relevance. Try this
for a non-fiction taste:
https://fora.tv/2008/08/08/Daniel_Suarez_Daemon_Bot-Mediated_Reality
– dan
Reply to Hal Finney,
2009-1-25 15:47:10 UTC
Hal Finney wrote:
- Spammer botnets could burn through pay-per-send email filters
trivially
If POW tokens do become useful, and especially if they become money,
machines will no longer sit idle. Users will expect their computers to
be earning them money (assuming the reward is greater than the cost to
operate). A computer whose earnings are being stolen by a botnet will be
more noticeable to its owner than is the case today, hence we might
expect that in that world, users will work harder to maintain their
computers and clean them of botnet infestations.
Another factor that would mitigate spam if POW tokens have value:
there would be a profit motive for people to set up massive quantities
of fake e-mail accounts to harvest POW tokens from spam. They'd
essentially be reverse-spamming the spammers with automated mailboxes
that collect their POW and don't read the message. The ratio of fake
mailboxes to real people could become too high for spam to be cost
effective.
The process has the potential to establish the POW token's value in
the first place, since spammers that don't have a botnet could buy
tokens from harvesters. While the buying back would temporarily let more
spam through, it would only hasten the self-defeating cycle leading to
too many harvesters exploiting the spammers.
Interestingly, one of the e-gold systems already has a form of spam
called "dusting". Spammers send a tiny amount of gold dust in order to
put a spam message in the transaction's comment field. If the system let
users configure the minimum payment they're willing to receive, or at
least the minimum that can have a message with it, users could set how
much they're willing to get paid to receive spam.
Satoshi Nakamoto
Bitcoin v0.1 release discussions from Cryptography mailing list
2009 Jan 25 See all postsSatoshi Nakamoto
satoshinakamotonetwork@proton.me
https://satoshinakamoto.network
I have put the Bitcoin v0.1 release announcement on the Cryptography mailing list about 3 weeks ago, here are some discussions from Hal Finney, Jonathan Thornburg, etc.
Bitcoin v0.1 released, 2009-01-08 19:27:40 UTC
Announcing the first release of Bitcoin, a new electronic cash system that uses a peer-to-peer network to prevent double-spending. It's completely decentralized with no server or central authority.
Here are 3 screenshots of the client's UI.
Download link:
https://downloads.sourceforge.net/bitcoin/bitcoin-0.1.0.rar
Windows only for now. Open source C++ code is included.
If you can keep a node running that accepts incoming connections, you'll really be helping the network a lot. Port 8333 on your firewall needs to be open to receive incoming connections.
The software is still alpha and experimental. There's no guarantee the system's state won't have to be restarted at some point if it becomes necessary, although I've done everything I can to build in extensibility and versioning.
You can get coins by getting someone to send you some, or turn on Options->Generate Coins to run a node and generate blocks. I made the proof-of-work difficulty ridiculously easy to start with, so for a little while in the beginning a typical PC will be able to generate coins in just a few hours. It'll get a lot harder when competition makes the automatic adjustment drive up the difficulty. Generated coins must wait 120 blocks to mature before they can be spent.
There are two ways to send money. If the recipient is online, you can enter their IP address and it will connect, get a new public key and send the transaction with comments. If the recipient is not online, it is possible to send to their Bitcoin address, which is a hash of their public key that they give you. They'll receive the transaction the next time they connect and get the block it's in. This method has the disadvantage that no comment information is sent, and a bit of privacy may be lost if the address is used multiple times, but it is a useful alternative if both users can't be online at the same time or the recipient can't receive incoming connections.
Total circulation will be 21,000,000 coins. It'll be distributed to network nodes when they make blocks, with the amount cut in half every 4 years.
first 4 years: 10,500,000 coins
next 4 years: 5,250,000 coins
next 4 years: 2,625,000 coins
next 4 years: 1,312,500 coins
etc...
When that runs out, the system can support transaction fees if needed. It's based on open market competition, and there will probably always be nodes willing to process transactions for free.
Satoshi Nakamoto
From: Hal Finney, 2009-1-11, 02:22:01 UTC
Satoshi Nakamoto writes:
Congratulations to Satoshi on this first alpha release. I am looking forward to trying it out.
It's interesting that the system can be configured to only allow a certain maximum number of coins ever to be generated. I guess the idea is that the amount of work needed to generate a new coin will become more difficult as time goes on.
One immediate problem with any new currency is how to value it. Even ignoring the practical problem that virtually no one will accept it at first, there is still a difficulty in coming up with a reasonable argument in favor of a particular non-zero value for the coins.
As an amusing thought experiment, imagine that Bitcoin is successful and becomes the dominant payment system in use throughout the world. Then the total value of the currency should be equal to the total value of all the wealth in the world. Current estimates of total worldwide household wealth that I have found range from $100 trillion to $300 trillion. With 20 million coins, that gives each coin a value of about $10 million.
So the possibility of generating coins today with a few cents of compute time may be quite a good bet, with a payoff of something like 100 million to 1! Even if the odds of Bitcoin succeeding to this degree are slim, are they really 100 million to one against? Something to think about...
Hal
Reply to Dustin D. Trammell, 2009-1-16, 16:03:14 UTC
I would be surprised if 10 years from now we're not using electronic currency in some way, now that we know a way to do it that won't inevitably get dumbed down when the trusted third party gets cold feet.
It could get started in a narrow niche like reward points, donation tokens, currency for a game or micropayments for adult sites. Initially it can be used in proof-of-work applications for services that could almost be free but not quite.
It can already be used for pay-to-send e-mail. The send dialog is resizeable and you can enter as long of a message as you like. It's sent directly when it connects. The recipient doubleclicks on the transaction to see the full message. If someone famous is getting more e-mail than they can read, but would still like to have a way for fans to contact them, they could set up Bitcoin and give out the IP address on their website. "Send X bitcoins to my priority hotline at this IP and I'll read the message personally."
Subscription sites that need some extra proof-of-work for their free trial so it doesn't cannibalize subscriptions could charge bitcoins for the trial.
It might make sense just to get some in case it catches on. If enough people think the same way, that becomes a self fulfilling prophecy. Once it gets bootstrapped, there are so many applications if you could effortlessly pay a few cents to a website as easily as dropping coins in a vending machine.
Satoshi Nakamoto
https://www.bitcoin.org
From: Jonathan Thornburg, 2009-1-17, 16:49:45 UTC
On Sat, 17 Jan 2009, Satoshi Nakamoto wrote:
In the modern world, no major government wants to allow untracable international financial transactions above some fairly modest size thresholds. (The usual catch-phrases are things like "laundering drug money", "tax evasion", and/or "financing terrorist groups".) To this end, electronic financial transactions are currently monitored by various governments & their agencies, and any but the smallest of transactions now come with various ID requirements for the humans on each end.
But if each machine in a million-node botnet sends 10 cents to a randomly chosen machine in another botnet on the other side of the world, you've just moved $100K, in a way that seems very hard to trace. To me, this means that no major government is likely to allow Bitcoin in its present form to operate on a large scale.
I also worry about other "domestic" ways nasty people could exploit a widespread Bitcoin deployment:
Is there something obvious I've missed? Is there a clever aspect of the design which prevents botnets from exploiting the system? Is there a way for every major government to monitor all Bitcoin transactions to watch for botnet-to-botnet sending?
– From: "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy, Indiana University, Bloomington, Indiana, USA "Washing one's hands of the conflict between the powerful and the powerless means to side with the powerful, not to be neutral."
– quote by Freire / poster by Oxfam
From: Hal Finney, 2009-1-14 16:48:03 UTC
Jonathan Thornburg writes:
Certainly a valid point, and one which has been widely discussed in the debates over the years about electronic cash. Bitcoin has a couple of things going for it: one is that it is distributed, with no single point of failure, no "mint", no company with officers that can be subpoenaed and arrested and shut down. It is more like a P2P network, and as we have seen, despite degrees of at least governmental distaste, those are still around.
Bitcoin could also conceivably operate in a less anonymous mode, with transfers being linked to individuals, rather than single-use keys. It would still be useful to have a large scale, decentralized electronic payment system.
It also might be possible to refactor and restructure Bitcoin to separate out the key new idea, a decentralized, global, irreversible transaction database. Such a functionality might be useful for other purposes. Once it exists, using it to record monetary transfers would be a sort of side effect and might be harder to shut down.
It's important to understand that the proof-of-work (POW) aspect of Bitcoin is primarily oriented around ensuring the soundness of the historical transaction database. Each Bitcoin data block records a set of transactions, and includes a hash collision. Subsequent data blocks have their own transactions, their own collisions, and also chain to all earlier hashes. The result is that once a block is "buried" under enough new blocks, it is essentially certain (given the threat model, namely that attackers cannot muster more than X% of the compute power of legitimate node operators) that old transactions can't be reversed.
Creating new coins is indeed currently also being done by POW, but I think that is seen as a temporary expedient, and in fact the current software phases that out over several years. Hence worries about botnets being able to manufacture large quantities of POW tokens are only a temporary concern, in the context of Bitcoin.
There have been a number of discussions in the past about POW tokens as anti spam measures, given the botnet threat. References are available from "Proof-of-work system" on Wikipedia. Analyses have yielded mixed results, depending on the assumptions and system design.
If POW tokens do become useful, and especially if they become money, machines will no longer sit idle. Users will expect their computers to be earning them money (assuming the reward is greater than the cost to operate). A computer whose earnings are being stolen by a botnet will be more noticeable to its owner than is the case today, hence we might expect that in that world, users will work harder to maintain their computers and clean them of botnet infestations.
Countermeasures by botnet operators would include moderating their take, perhaps only stealing 10% of the productive capacity of invaded computers, so that their owners would be unlikely to notice. This kind of thinking quickly degenerates into unreliable speculation, but it points out the difficulties of analyzing the full ramifications of a world where POW tokens are valuble.
Hal Finney
From: Bill Frantz, 2009-1-24 23:22:21 UTC
hal at finney.org ("Hal Finney") on Saturday, January 24, 2009 wrote:
Some people tell me that the 0wned machines are among the most secure on the network because botnet operators work hard to keep others from compromising "their" machines. I could see the operators moving toward being legitimate security firms, protecting computers against compromise in exchange for some of the proof of work (POW) money.
Cheers - Bill
Bill Frantz | When it comes to the world | Periwinkle
(408)356-8506 | around us, is there any choice | 16345 Englewood Ave
www.pwpconsult.com | but to explore? - Lisa Randall | Los Gatos, CA 95032
From: dan at geer.org, 2009-1-25 04:07:17 UTC
Bill Frantz writes:
I'm one of those people. Quoting from my speech of 1/20:
Rest of text upon request. Incidentally, I highly recommend Daniel Suarez's Daemon; trust me as to its relevance. Try this for a non-fiction taste:
https://fora.tv/2008/08/08/Daniel_Suarez_Daemon_Bot-Mediated_Reality
– dan
Reply to Hal Finney, 2009-1-25 15:47:10 UTC
Hal Finney wrote:
Another factor that would mitigate spam if POW tokens have value: there would be a profit motive for people to set up massive quantities of fake e-mail accounts to harvest POW tokens from spam. They'd essentially be reverse-spamming the spammers with automated mailboxes that collect their POW and don't read the message. The ratio of fake mailboxes to real people could become too high for spam to be cost effective.
The process has the potential to establish the POW token's value in the first place, since spammers that don't have a botnet could buy tokens from harvesters. While the buying back would temporarily let more spam through, it would only hasten the self-defeating cycle leading to too many harvesters exploiting the spammers.
Interestingly, one of the e-gold systems already has a form of spam called "dusting". Spammers send a tiny amount of gold dust in order to put a spam message in the transaction's comment field. If the system let users configure the minimum payment they're willing to receive, or at least the minimum that can have a message with it, users could set how much they're willing to get paid to receive spam.
Satoshi Nakamoto