Is 18 really the best age of consent?

I've seen lots of posts pointing out redditors complaining about the american age of consent(a lot of them sounded like the typical reddit jerk though). As someone living in one of those blue countries (http://i.imgur.com/WIwRY.png), I don't believe that's absurd at all, but, admittedly, I've never thought of the subject that much. Anyway, I would just like to hear some opinions.