Spammers suck, but the real blame lies with their customers: if spamming didn't work, nobody would do it.
Instead of the current crop of half-assed anti-spam measures that often throw the baby out with the bath water (such as rejecting mail originating from residential IP blocks), I propose a new approach: ISPs maintain a database of URLs that are linked to in spam messages. A proxy or customized browser detects when a user attempts to load an offending address and pops up a big, honkin' dialog box that says something like
You are about to visit a Web site belonging to a spammer. By continuing, you will be actively contributing to making the Internet worse for everybody, including yourself. Are you sure you want to do this?
[ Hell No! Screw the Spammers! ] [ I Am An Asshole, Continue Anyway ]
I think this would be far more effective, and those of us who want or need to run our own SMTP servers could do so again.
UPDATE
AOL is now blocking access to spammer sites