Just got back from Bonaire last month and they had one at Houston IA (GHWBIA) and watched a woman go in and the alarms went off to do a further search at which time the Supervisor told her to go through and was cussing about the damn machine and how inaccurate it was! "We are getting all kinds of error messages" he said on a radio to someone!
So not only invasion of privacy, but expensive crap that doesn't work! Wait till they are in charge of Health care! We are about to turn a hug corner in this country and it will make the inconvenience of traveling look like a walk in the park!