Blue Security maintains a Do Not Intrude Registry containing email addresses that community members which to protect.
Blue Security also accepts spam reports from members for analysis and then sends the offending merchant and ISP a request to stop spamming.
Where they differ from other services like Spamcop is each community member runs a Blue Frog client that automates posting opt-out requests. If the merchant continues to send out spam, Blue Security writes a script that tells the Blue Frog client how to submit a complaint on the merchant's website. Then the more spam the merchant sends out to community members, the more opt-out requests the website gets, until it gets overloaded and crashes.
Anyway, this antispam scheme seems to be working for now, but who knows how long it will be before they get sued by spammers. (It happened to Spamcop.)
I finished downloading all my Gmail email via POP this evening, so I backed it all up to CD-R. For the 14 months I've been on Gmail, I have 31,652 emails taking up about 240MB. Not that much, but then again, I have been deleting some email that I don't need, contrary to Gmail's recommendation to keep everything.