What’s more appealing to a loathsome spammer than a webpage that they can post anything they want to? That’s how they see blogs and their comments they use to promote themselves and vandalize your website. Bloggers have fought back with tools to fight programs that scan the net looking for blogs they can spam comments to. There’s a plug-in for MovableType called MT-Blacklist. Ben and Mena over at SixApart give a great outline of the whole problem.