IMO there are two kinds of friendzones:
1) Annoying guys finding a scapegoat for when they can't get laid
2) When you're the kind of friend with someone that you wouldn't want to risk losing in a relationship
So I've been put into the 2nd one a fair amount. Never really had experience with the first either way.
As far as rejecting people, it's happened like once or twice but I'm by no means someone everyone goes after, lol.