I've seen people do equivalent things plenty of times. A group of people at my dorm (guys and girls) conned some poor kid on IRC, got him to reveal embarrassing sexual things about himself, and passed around screen shots. In high school, a girl would go to a guy and say that some other girl wanted her to tell him that she liked him, just so people could be entertained by the consequences. People lose their taste for that as they grow up, but for every kind of growing up there are people who never do. They just become more sophisticated. I've had people reveal private things about other people to me that made my blood run cold at the cruelty required to spread such information, and only for a trivial social advantage.
Adults who act that way are apparently rare and not well-liked, but odds are you know a few. You teach a child to be wary when approached by a stranger offering unsolicited favors, but not to be afraid of approaching strangers when they need help. The same principle applies when you are contacted anonymously over the internet and asked to reveal intimate emotional secrets.
I agree that becoming withdrawn and inhibited is not the best defense (the best defense is simply being someone other people will stick up for) but the site is targeted at people who cope with social fears by being extremely risk-averse. If you have to be comfortable with the risk of exposure and ridicule in order to use the site, then what's the point, except to be a fun flirty thing for cool people for fifteen minutes? The target users need some assurance that the site delivers on its promise of a less-risky way of revealing their feelings about somebody. Perhaps you're right that they shouldn't, but they do, and that's what matters.
If you're dealing with somebody new, you shouldn't assume they're out to get you. If you're dealing with everybody, you should assume somebody's trying to get you.
