I don't think they click ads, I see friends checking out ads all the time. Particularly music ads. I'd imagine that it's not just a small-time thing, considering they're in the green now, but perhaps that money's coming from something else.

Their ads are also a lot better than they were a year ago. They target more effectively, within reason. (My ads are screwy since I list no information about myself, but they used to try and sell me Arrested Development t-shirts and they almost succeeded on multiple occasions.)