The Penny Black project is looking for ways to block spam. At the source.

"The Penny Black project is investigating several techniques to reduce spam by making the sender pay. We're considering several currencies for payment: CPU cycles, memory cycles, Turing tests (proof that a human was involved), and plain old cash. There are multiple system organizations that can support this: senders can pre-compute the appropriate function, tied to a particular message; senders can come up with the payment in response to a challenge after they've submitted their message; senders can acquire a ticket pre-authorizing the message. Recipients would aggressively white-list good senders.

The ticket scheme involves creating a ticket service that would issue tickets, which can then be submitted with an email message. The recipient would then call the ticket service to validate and cancel the ticket. There are some interesting ramifications to the ticket server idea. For example, 1000 pre-paid tickets might be bundled with each new PC."

Please note that projects developed by Microsoft Research might not reach the streets. They're studies and prototypes. This project brings new concepts... But would it be for the good, even ot get rid of the evil?