> Read an article (in an ACM transactions, I believe) about 
> such a system
> - each user would many virtual mailboxes. Unprivileged 
> writers would only know the basic public box, which would 
> discard any message not bearing a stamp (some form of 
> micropayment). After you recognize a friend has sent you a 
> stamped message, the polite thing to do is of course to 
> return the stamp along with a priviledged sub-address that 
> doesn't require a stamp.

If you can find the article again, I'd like to read it (which issue?).
It'd be nice to have the same scheme applied to the telephone as well
(and probably instant messages too).

- Stephen