No, really:

[E]ven more scary than that is the article notes that the TSA admits that it’s really bad at finding weapons, saying that the “failure rate” of tests is reaching 70% at some major airports and at some airports “every test gun, bomb part or knife got past screeners.” So, while scanners are looking at or touching your crotch, they’re apparently not bothering to look for guns. Comforting.