I've enabled word verification in my comments. What this means is that anyone commenting in my blogs has to pass word verification similar to when you created a blog before your comment will post. I did this in response to 3 spam comments in one of my posts, the word verification cuts down on automatic comment spam.
To enable this in your blog go to Dashboard>Settings>Comments then click yes at word verification.
Me, I'd rather go the extra step like that instead of getting spam.