[gdne]

Already been tried. It's called hashcash: http://www.hashcash.org/

Coincidentally, hashcash's proof of work is the foundation of bitcoin.

But don't let this discourage you from trying your idea. I think it's still a fantastic idea. Making email cost something to send (either btc or CPU time like hashcash) would kill spam, and slow down the flow of over-communication.

[vezzy-fnord]

The merits of charging CPU time are arguable, but adding monetary costs to sending email is absolutely immoral. Especially something like Bitcoin, which has a steep learning curve.

Unless your goal is to transform email into a system more closely resembling snail mail, but for cipherpunks.