Deflexion.com

In the article
The Spam Wars: How should the Internet deal with junk mail?
at Reason,
Wendy M. Grossman says:

There’s one more approach to the spam problem that we should consider. For the lack of a better term, we might call it the community solution. Alternatively, we could call it the Usenet approach.



Created in 1979, Usenet is in many respects still the town square of the Internet. It played that role even more in 1994, when the Web was still in its "before" stage and two Arizona lawyers, Martha Siegel and Laurence Canter, sent out an infamous spam advertising their services, provoking a furious reaction. The technical method used to post the message meant that you couldn’t mark it read in one newsgroup and then not see it in the others, so anyone reading a number of Usenet newsgroups saw the message in every single group.



. . . In the ad hoc newsgroup news.admin.net-abuse.usenet, users and administrators discussed and developed a system that took advantage of the cancellation features built into Usenet’s design. These are primarily designed so people can cancel their own messages, but a number of public-spirited people hacked them so third parties could use them to cancel spam.



By now spam has died out in many newsgroups, . . .

This is one of the reasons that I think NNTP -- the protocol used by Usenet newsgroups -- is the way to go for discussion groups or any type of shared (non-personal) "mailbox."
Collaborative filtering works well in this distributed system. For an idea of what I mean, check out the "This is Spam" button
in the Loom interface to gmane.org.infiniteink (but don't click it unless a message really is spam!).
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