AllSpammedOut writes: "Spam could be more easily detected if everyone were
to compare the mail messages they received. Using the Distributed
Checksum Clearinghouse, MTAs can report the checksums for all messages
they receive and be notified when a checksum has already been reported by many other systems."
Obviously there are issues with something like this (especially mailing lists, and worms that do attachments). I suspect spammers would just include a counter to break checksums tho."