It doesn't work because it was conceptualized as a search for weapons -- or anything that might be used as a weapon. On Christmas Day you can bet TSA agents confiscated plenty of nail files and toothpaste, even if they did miss the explosives in Umar's undershorts.
Adopt a Quasi-Israeli Model: There is widespread consensus that the Israelis have developed a more effective approach to airport security: Their priority is to find the terrorists, rather than the weapons. They have smart, well-trained agents asking passengers simple questions. The answers lead either to reassurance - or suspicion.
The problem with this approach is scalability. The Israelis question everybody but they have only one main airport and one main airline. The United States has millions of passengers coming and going through hundreds of airports on scores of airlines. But perhaps there's a way to apply the general principle: Have a relatively small number of TSA agents "walking the beat" at airports, taking advantage of the time passengers spend waiting on line to check in, waiting on line to pass through security, and waiting at the gate.
Agents would be informed of any passengers whose names are on watch lists at any level and they'd ...well, watch them. They'd look at other passengers too. They'd be trained to look for behavioral clues. Experienced suicide-bombers are few and far between. (Think about it.) That means most may not be able to coolly settle back with a John Grisham novel. They may be nervous or seem dazed as they contemplate what they are about to do. There may be "tells" in how they sit, move and relate to other passengers.