Haha, nothing to stop the junk except the "Next" button. Maybe some auto-rating based on time spent in a pairing session? Assumption being longer sessions mean useful work is getting done, but quick skips mean some doofus was showing his junk.
I just don't think much would get done if you were just on there finding people that may or may not have anything in common.
I think the face vs. desktop thing should be A/B tested. It could go either way.