People tend to be extremely indiscreet on these public networks. You'd learn a lot about them even if you weren't nosy.

[He is quite possibly the nosiest person ever to live -- if something can capture his interest. If not, he's indifferent. But his inquisitive nature has usually paid off, and when it doesn't, when someone seems evasive, especially needlessly evasive... that in itself is usually a clue.]

What sort of superpower would you want to have?