The concept of friend zoning is weird to me because you start off as a friend, if things move on to the next level then you were boyfriend/girlfriend zoned. Feeling like you got friend zoned by a girl (sticking with one gender to make this easier) you were either on casual terms or friends with only tells me that once the guy finds out he's only like the brother or friend to a girl he had expectations. Very realistic case, don't get me wrong, I understand that this is how the majority thinks. Me, personally, a guy starts in the friend zone because I need to know what kind of person he is first.
Then again, there are people who believe the opposite sex can't be friends. I agree with this somewhat, because you'll end up wanting more with the person you're compatible with. It's a dangerous game to play, because the person that wants to advance the relationship but can't, hence friend zoned, will always be the victim.