The inimitable Bruce Schneier just posted about how the response to the LA bomb theats was an incident of "CYA security" -- the purpose of which is not to make a community more secure but to insulate authorities from blame: He first discussed that topic back in 2007, and the post remains all to relevant:
If someone left a backpack full of explosives in a crowded movie theater, or detonated a truck bomb in the middle of a tunnel, no one would demand to know why the police hadn't noticed it beforehand. But if a weird device with blinking lights and wires turned out to be a bomb -- what every movie bomb looks like -- there would be inquiries and demands for resignations. It took the police two weeks to notice the Mooninite blinkies, but once they did, they overreacted because their jobs were at stake.
This is "Cover Your Ass" security, and unfortunately it's very common.