The Transportation Security Administration did not officially start requiring travelers to take off their shoes at the airport until August 2006. That was nearly five years after Richard Reid unsuccessfully tried to ignite explosives in his sneakers on an American Airlines flight from Paris to Miami. The fear of Reid copycats was the ostensible justification for the TSA's seemingly belated shoe rule, which the agency finally ditched last week, nearly two decades after adopting it. The longevity of that widely resented and ridiculed policy, which the U.S. was nearly alone in enforcing, illustrates the ratchet effect at work in security...