What I’d love to see is an email-like system where each message is accompanied by a small sum of money (1¢ or so). If the message is not useful to the recipient, they are free to take the 1¢, otherwise, if the message is useful, they wouldn’t (and it will return to the sender either when the email is replied to, or, say, in a week). This would very quickly kill all spam-type business models, and would be unlikely to cost anything for legitimate users.