Just how bad an idea is the plan by the mayor of New York, Michael Bloomberg, to limit the size of sugary-drink cups (okay, pails? Buckets? Delivery devices?) to 16 ounces? Even the big-government left is lining up against the proposal. Imposing this regulation, writes Ira Stoll, is an act of arrogance, not only when it comes to the confidence in the ability to draw such apparently arbitrary distinctions, but when it comes to the role of government.