With a bit more on the "automated comment spam" front, Harry Fuecks has a new post - Comment Spam Compiled and Interpreted - that might help to clear a few things up.

Following on from Automated Blog Comment Spam? and the feedback (many thanks), figured I'd compile (and interpret) some of it into something more ordered.

He separates it into topics including: "Gnomes or Robots?", "No Bars to Legitimate Use", "Preventing Automation", "Blacklisting", "Remove the Incentive", and "Economics". Each topic gives several ways/ideas on how they can help you and your blog avoid the comment spam that seems to be running rampant on the internet these days. There are also a boatload of links in each section to help with the understanding of each concept.