I've said for a while now that spam would be a much smaller problem if every e-mail sent cost 1/100¢. Normal users wouldn't notice the charges (how many e-mails do you really send?), but massive spam-bot orgs couldn't hope to pay the fees. Really, of all the ways that advertisers can spam (junk mail, telemarketing, flyers, TV commercials), e-mail is the only medium that is essentially cost-free.

Actually, now that Amazon has its "Requester Pays" system, I'm just waiting for someone to setup a messaging service that charges fees to send me something (think encryption key stored on S3 that must be payed for and downloaded before e-mail can be sent to me).

As soon as someone started trying to charge for email, a new email system would arise. Who would you be paying?

You'd be paying for the privilege of not getting spam. In my hypothetical scheme, you'd be paying Amazon for transfer of the key and whoever setup the system to generate the key. Also, I would expect most people would end up paying less than the equivalent of one latte/month. It's only the spammers who (one hopes) wouldn't be able to afford it...

For sure - with all those pesky users gone, their servers should have no more scaling problems.