Maybe if there was some way of voting spammers off? If all users who've been here more than 3 months and made more than 10 posts got a 'this is spam' button when we read a new post, which could be used to remove the offending post if enough of us click it. Get three posts voted as spam within a week and that user gets deleted as well. If the votes required are carefully chosen to be an appropriate proportion of the usual daily visitors, there would be virtually no risk of abuse.
Also if the *same* message is posted to three or more forums during their first 24 hours membership they are a cut & paste spammer and the best solution is to auto-wipe their posts and account. You'd also need to ban the IP address. It would be best to delay the wipe five minutes or so so they *think* its worked and dont work out how to defeat it,
Remember, Spammers are Stupid, so it doesn't take much to program the server to be more intelligent than them . . . .