Apparently, if Ben Popper's article in the Observer is to be believed, the hotties on dating sites are not the ones who are the most sought after...
It's the ones who are cute, but certain guys find unattractive.
It makes sense. From personal experience, I rarely try to chat up the most gorgeous girl at a party. Not that I haven't gone out with some extremely beautiful women, but as a guy on the prowl, I know how important it is to punch your weight. I therefore usually wind up talking to the "undervalued" females (as Popper puts it). These are people I know are cute and attractive, but I also recognize are not univerally seen as such.
Which, ironically enough, makes me think that this provides schlubs on the prowl with an opening: Maybe you should talk to the most beautiful girl in the bar if all her less-than-stunning friends are being monopolized.