I posted this in another thread recently.

The TSA did a test of its behavioral profiling where they set up a guy behind the ID checkers at a dozen or so airports during the holidays. Based on watching pax interact with the ID checker, they pulled over 500 people to talk to. People were either let go, sent for secondary, or sent for secondary and an LEO was called, depending on how "suspicious" they were.

Just under 30 people end up getting nailed for something. No terrorists, of course. Mostly people who had outstanding warrants, "too much" money or drugs.

30/500 = 6%

That's not a bad percentage, but the problem is that 99.9999999% of the people they catch are going to be people who are no threat to aviation security, but have "too much" money on them or something of the like. If we were just trying to catch criminals this might be a good idea (and I'm totally against using the checkpoint for that purpose), but I'm not sure how valuable it would be in catching terrorists.