I've turned on the word verification in my comments. What this means is that anyone leaving a comment has to pass the word verification before their comment will be posted-it's similar to the word verification you do when you create a blog. This cuts out on automatic comment spam.
I didn't know this existed until I posted at Crochetville about getting 3 spam comments in one of my blog entries.
To enable this, go to your Dashboard>Settings>Comments then click yes for word verification.
I would rather go this extra step in comments on anyone's blog than have them get spam.