I guess we just have to be diligent about ratting out and kicking off these slimy, good-for-nothing, low-life, scumbags, until they learn that it's useless. Personally, I think that a couple of public executions would slow it down tremendously. LOL.
By the way, at work, we use something called a Barracuda (How fitting is that?). It somehow monitors the internet traffic and removes all of the spam email. It updates itself every hour automatically, to handle new threats. It's too bad that they don't have something like that for online forums (Maybe they do, I don't know).