I can't second this. If there would be a worldwide micropayment system then I would happily pay a cent or two for a email to save me from spam. (Hey you pay that ten times for sending a SMS.)

Yes, but for having it work for you, the people sending you email have to be willing to pay for email.

Considering the the huge success of "sharing" cracked games, DVDs and CDs to avoid paying for them, or for VoIP to avoid costs, I don't think having to pay for one of the killer-applications of the internet, a service that has been free for over three decades, is going to be a success. Specially since it would be trivial to have a legal, cost-free, alternative (everyone has it already).