TSA policies offend, but do they work?

Does the TSA get useful results? It's an interesting question, and not an easy one to get to the bottom of, according to Slate's "Explainer" column. Short answer: There's evidence that they do catch the "random nuts", as well as drug smugglers and illegal immigrants. (In the case of the latter, by using techniques similar to the Israeli visual behavior profiling system that's been brought up in the comments here several times). But the big game? Actual, honest-to-jihad terrorists? There's really no evidence available about that, one way or the other.