A NYT editorial suggests "If banks or credit card companies refused to settle payments with spammers' banks, they could disrupt spam."
see:
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Reasonable idea? IMHO, many of the problems we face today in the "e-world" are due to the lack of controls once common in the world of commerce. Of course, those lack of controls enable a very high volume of commerce and no one wants to be the one to say "the party's over, it's time to go home".
(For instance, just the other day I ordered stuff over the telephone giving my credit card number orally. In the old days I'd have to mail in an order form and check and the business would have to wait until the check cleared.)