Imagine, a spam email message lands in your email, you click delete and it disappears from your Inbox - and the Inbox of your family, your friends and the entire world. Cloudmark SpamNet is a worldwide spam-fighting community that gives you spam-free email just for deleting the spam from your own Inbox. Join SpamNet now and contribute to the global fight against spam.
Although spam seems to be invading everyone's email, only a relatively small number of spammers send out the billions of spam messages polluting the Internet. By reporting the spam you receive, you will contribute to the growing community of spam fighters dedicated to eradicating spam.
Just like Napster allowed us to share our favorite music, Cloudmark SpamNet allows us to share the spam we receive. Individually this reported spam isn't very powerful, but the collective reports of millions of email users networked together blocks virtually all spam on the Internet.
Sounds pretty interesting. Not exactly sure how it does it (how it identifies the spam exactly as a match to one that was deleted by a user), but certainly something to look into.