Comment spam is evil. I've been getting on the tune of 25-50 comment spams per day the past several weeks. My custom utility to quickly delete comments in .Text has helped delete comment spams after the fact; additionally, SQL triggers have, to date, proactively nuked over 20,700 comment spams (although they have also stopped valid posters who have added common spam 'keywords' to their posts).
Since the SQL triggers are clearly no longer working, I'm going to give CAPTCHAs a try. In theory, CAPTCHAs can be broken... easily. However, I'm hoping/assuming that the vast majority of scum known as comment spammers aren't using programs that can decode CAPTCHAs and aren't using the social engineering/free pr0n!! techniques detailed here. Rather, I'm assuming a scant few of the comment spams (the ones I get like one or two of a day) are entered by actual humans; the majority, of which I get a blast of, say, 30 in a five second period, are probably coming from a pretty dumb HTTP screen scraping/HTTP posting program. If my assumptions are sound, then the CAPTCHA ought to drastically reduce the amount of comment spam appearing on my blog.
I've taken down my comment spam-related triggers and replaced them with Miguel Jimenez's free Clearscreen SharpHIP CAPTCHA Control. The nice thing about this control is that it automatically checks for validity on postback so it integrates with .Text without having to modify the codebase. One downside, however, is that any other postback sections on the web page will no longer work unless the CAPTCHA is filled out (you may have noticed the blog entry rating feature has been removed).
Hopefully the CAPTCHA cuts down on the comment spam, as having to wade through and delete 50+ comments every day or two is really started to get mundane and annoying. (I do take removing comment spam seriously, though. I challenge you to find a single piece of irrefutable spam in one of my blog entries that's older than, say, a week.)