I agree with Yomi. Akismet occasionally filters out actual blog comments as spam. I remember commenting on one of my friend's blogs and they never received the comment. Then, they later told me that they found it under 'spam'. Which was really weird because I don't even comment on blogs often, and I certainly didn't even use that email address much. I had to write to Aksimet, telling them to remove my email address from their spam database because I'm not a spammer. They apologized and removed my email from their database.
Nevertheless, Akismet is top-notch. But I've stopped using the comment section on my blogs. I noticed that most people just use it to promote their own websites. I prefer using the Facebook comment API. You're more likely to receive comments from actual people instead of spam bots or spammers.