Tim Bray has an idea for killing spam - it's the pay for email variant (each message costs some small amount of money to send). The only problem with the idea is that - as with most such ideas - it could easily be defeated by some unscrupulous set of offshore operators. All it would take to get around it is someone willing to charge less than the typical rate and willing to accept spammers. He has the whole digital signature and certification idea for working around that, but I don't buy it - I just don't see all email systems going to this model simultaneously, and that's what it would take. In the meantime, some of his anecdotes explain why I still don't use a spam killer - I'd rather hand delete the stuff than try to figure out what I've lost.