As to the difference between planes, trains and automobiles, it's a safe bet almost no one on a dock by Lake Pontchartrain arrived from Libya a few hours ago. YOU may not be traveling to or from an overseas destination, but a lot of the people you were rubbing shoulders with at Logan today were. The first time a train or boat is deliberately detonated en route, killing thousands, you'll likely see similar security levels for those means of travel, too.

The reason the new security measures aren't a civil liberties violation, however, is even more basic: If you tell TSA you won't submit to either a pat down OR backscatter machine, they can't legally force you--you just can't get on the plane. Whether in an airport terminal or on the sidewalk, if a cop tries to pat you down with neither a warrant nor probable cause, and you refuse, he's breaking the law if he does it anyway. Of course, my (personal and other) experience has been that, even on the street, if you assert your Fourth Amendment rights when a search is requested the cop will just provide some specious rationalized probable cause and do it anyway, so I'd say TSA is the least of your worries, citizen.