I'm not concerned about my bulbous naughty parts being seen by some TSA agent, but I am concerned about the possible ill effects of being scanned by those machines 10 times a year or more.   The input I've heard and read from experts tells me that the safety of such frequent exposure has not been demonstrated.

I also don't believe the scanners will prevent a terrorist blowing up a plane, so I think it's a great inconvenience, invasion of privacy -- we're going to have teenagers undergo virtual strip searches too? --, and potential serious health risk, without really making us safe anyway.