You've had the experience of walking along and negotiating around someone who is walking slowly, weaving or bumping into other pedestrians for an obvious reason: He or she is talking on a cell phone, listening to an iPod or texting on a Blackberry. And you've had the natural, inevitable response to this annoyance: demanding a law to prevent it. ... These measures reflect a reflexive urge to regulate even the smallest elements of human behavior, from the flavorings in cigarettes to the type of fats in restaurant meals to the number of bullets a magazine may hold.