It's because of your personality. That you would speak negatively about your friends in favor of your own ego, even if it is to a forum full of strangers, is an indicator that you have some inner flaws and it is most likely centered around ego.
Don't worry about what other people are doing. And if you want good friendships, keep any negative gossip or even negative thinking about them to a minimum. You probably wouldn't want them posting on a forum about how they have better personalities than you (which, judging by the fact that they are uglier than you, not as fit as you, break all those rules and still manage to get girls... is probably true).
EDIT: plate beat me to it.