Do you use WordPress? If you do I find the best Comment spam defense is a good offense. Combine Akismet with a few other good Spam defenders and you could be free from that detestable comment spam!
I use WP-Hashcash
http://wordpress.org/extend/plugins/wp-hashcash/
Try it! Best thing about it is it doesn’t bother real users and kills bots dead.
After all Akismet is good but some of those spammers just get by Akismet since it is still based on user feedback.
Of course that doesn’t last long usually.
Like I said best defense is a one two punch offense. . . .
Akismet + WP-Hash Cash = Dead Comment Spam