Spam: The other white meat

I find it amazing that MT is so easy to spam. Many of the blogs that I have to pay attention to for work are basically honey pots for spammers. I've installed the MT Blacklist extension so that now most of the blogs that I run are protected, but the legacy of spam takes forever to pull out. I'm tempted to just delete all the comments in the system- one blog I'm dealing with had 8500 spams and no real comments that I could find. Ironically, what made me really start paying attention to this is the fact that we burn huge amounts of bandwidth serving pages with thousands of spams on them. This really bugs me.