Long time ago I made a reseach and found out at least 5 types of people:

Also, I found this on secretgeek.net: There's 2 reasons that a smart person should realise they are still, essentially, stupid. The obvious thing is that no matter how much you know, your knowledge is an insignificant compared with the sum total of what can be known. But here's the real kicker: every idiot in the world knows at least 1 or 2 things you don't know.