Comment spam and SEO
The guys at Akismet have an interesting article about how eliminating spam is good SEO. I’m not so sure about Google trying not to penalise sites with spam comments—I think Google are tougher than they make themselves out to be—but the rest of the article is worth a read.
On the subject of Akismet, it has stopped over 123,000 spam comments from reaching my blog, and currently blocks around 100/day on average. That’s quite impressive for a service which I pay nothing for and don’t have to maintain, other than the occasional plugin upgrade.