For the last few months I've had nothing but problems with blog spammers. I have run a few various systems for keeping the spam in check, and most of them have been quite successful. Unfortunately, they require quite a lot of maintenance and updating, so I have changed the comment spam prevention system to use Akismet. So far, it has caught every spam posted to the site with no false positives - excellent.
What I found disturbing, though, was when I visited the Akismet site and took a look at their stats. Apparently "93% of all comments are spam" now, a far higher proportion than I had thought previously. On AddedBytes.com the figure is about 85%, and rising. So much for the search engines' promise to deal with the problem!
AddedBytes.com is the online playground of 
http://www.gregphoto.net/index.php/2006/06/11/akismet-and-the-zend-framework