Also, what happens when a spammer cracks the login information for someone's account to a trusted relay and sends 6 million spams through it? The hacked victim would be stuck with the bill, and there would still be spam. A partial (and sane) solution would be for trusted relays to throttle outgoing mail depending on the client... then the spammers would need to crack a cooporate/mailing list account, and the owner of such an account would likely be more capable of taking legal action against the spammer.

just some thoughts...