This is definitely true. Plus, I think these are open to abuse. If the submissions are coming from a self-selected user base, surely its possible to self-servingly interpret certain statements as "predictions" that aren't, or a certain set of events as "proving" a prediction in one way or the other.

There is only so much fudging that can occur, of course. But this kind of on-the-margins behavior is a new challenge that this relatively new breed of sites will have to deal with.