Here's a bit of info on this, comparing full body MEDICAL scan risks to people who survived atomic bomb blasts:
http://crr.columbia.edu/reports2003/f3.htm There's no doubt more study needed, but as someone who's already had numerous CT and MRI scans in my lifetime, I don't want any more scans at the airport. Now they're talking about putting scanners into courthouses, bus and train stations, so it would become impossible to avoid them if you travel or your business requires you to go to court at times (as my work does). So are court reporters, journalists, attorneys, and judges to be groped every time they go to work, too?
Personally I think the first place they should install one is in front of Congress and make every legislator go through it on a daily basis or be groped. That would motivate them to find better solutions to protect our health and privacy.