Security expert Bruce Schneier has posted a great roundup of links to news stories and studies about the use of x-ray backscatter machines in airports.
Personally I do sympathize with the TSA’s charge to protect us from planes getting blown up or hijacked but think these machines go over the line. Here’s my simple test: imagine that instead of using these machines to take a naked x-ray picture of you, the TSA required you to step behind a screen and undress in front of one of their agents while they take your picture (which they claim they won’t retain).
I think we’d be far safer spending the $300-400 million we spent on these scanners to instead hire air marshals. As Schneier points out, the shoe and underwear bombers were caught by humans noticing something wrong, not machines.