A short history of airport security: We screen for guns and bombs, so the terrorists use box cutters. We confiscate box cutters and corkscrews, so they put explosives in their sneakers. We screen footwear, so they try to use liquids. We confiscate liquids, so they put PETN bombs in their underwear. We roll out full-body scanners, even though they wouldn’t have caught the Underwear Bomber, so they put a bomb in a printer cartridge. We ban printer cartridges over 16 ounces — the level of magical thinking here is amazing — and they’re going to do something else.
Bruce Schneir via A Waste of Money and Time – Room for Debate – NYTimes.com