A few people have posted that they have been forced to disable comments on their blog entries due to spam comments.
I'm having the same problem with my website's guestbook.
There seem to be a few bots going around scanning for Guestbook-esque URLS.
I see a single IP address test for a lots of CGI scripts, then shortly afterwards multiple distinct IP addresses post spamy links in my guestbook.
For the moment I've disabled the guestbook, and I will shortly remove links to it online.
I wonder if it's worth setting up a hack to run the comment against a spam filter? Or adding moderation? It's either that or add in some kinda image recognition test - but personally I'm not a big fan of those.
Mostly my guestbook doesn't get that much use anyway. Maybe 200 messages in a couple of years, but it's nice and friendly so it seems like giving in spam to lose it.