I was rather surprised to find comment spam in my blog (considering
it's new and relatively unknown), but then it was Outlook-specific spam
and I did have some Outlook-related blogposts.
Anyway in an attempt to fight it off I've enabled Movable-Type Blacklists as well as CAPTCHA images in the comments. I hope this isn't too annoying for you; if it is let me know and I'll remove it.