Well, it turns out there's such a thing now as comments spam--and some people have it.. See this post from Shelley at Burningbird:
The vig-rx blog virus, otherwise known as comment spammer, is using Google against us. After stealing another IP address, as expected.

Weblogs being targeted are being found through a Google search. Example is here. Aren't open web services a wonderful thing? Go ahead -- all open comment MT weblogs on this list have this comment, if they haven't deleted it yet. The key word in the search is Blog -- any weblog title or entry with Blog, and Bob's your uncle.

and a comment on the person doing this, from ralph: I looked at the logs shortly after posting my original comment and saw that indeed they got to my site through Google using the pattern you mention. There was a delay of about seven minutes between the original access and the posting of the comment. When I saw that, I realized the same thing you did in your recent post, that this clown is parsing the form, and that my form is indeed close enough to the "standard" way of doing things that his parsing works, even though the form elements all have different names than MT's. So the software he's using is not tied to a particular tool.