If I understand Bill Gates, what he actually wants is someone to pay MICROSOFT 10 cents for sending an email. I don't blame him, if I was smart enough, I'd do it.
No, I realize you might just be making a joke, but he was quite clear in his book that the money should go to the recipient. But regardless of that, I think it's a good idea. It would not only limit spam, it would also straighten out certain aquaintances and relatives who have a ten-to-one e-mail ratio.