Email postage to stop spam?

According to this article Bill Gates, among others, is suggesting that we start buying email stamps.

Sure, a penny per message would probably stop some spammers. But who's the postage money going to? To my ISP? To the recipients ISP? To the government? Maybe to me?

Hmm... If the money goes to me, then maybe all those virus writes will become rich because they would infect people's machines to send email to them (and thereby money)...

What about international spammers? Is there a particular reason why spammers wouldn't send spam from abroad? How in the world do you get the entire world to agree on email stamps? You would have to, otherwise there would always be some email stamp free paradise where the spammers can do their business from. Isn't that's what's called "offshoring"? :-p

Buying postage by solving a math puzzle? Sure, I love math puzzles, but what about people who aren't any good at math? Last time I checked, they could still buy stamps at the post office. Or would it be my computer that would be used as a client to compute something? Why should I trust something like that to be done on my machine?

Would all email go through email clearing centers? That would be one way of enforcing, right? In that case, why wouldn't the email clearing center just filter spam at no cost to me?

The article brings up another interesting point... If such email clearing centers did exist, what if they get hacked? Now I can't send or receive any email and my business grinds to a halt.

Also, if email becomes costly enough, then we'll get other solutions for getting our messages across pretty soon. Oh, wait... They already exist... Like MSN Messenger and the like.

Well, anyway, enough digressing about non-Borland related stuff. I hate spam just as much as the next guy, but I don't think buying stamps is the solution. It smells like paying for bandwidth to me...