Again, not condoning the invasion of privacy for security theater, but the "threat" of ionizing radiation is almost always over-stated.
High Penetration Model: (500/y/subject) < 2.0 uSv (0.2 mR) / per scan
An average human receives 10 uSv during an average day from background radiation, and 40 uSv on a cross-country flight. Living in Denver, CO for a year will expose you to 1800 uSv.
Some more dosages for various routine living situations and medical procedures (note, they are in mSv, not uSv): http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/Rad...
I was trying to imply that the argument of "it's not that bad" can quickly become moot considering that imaging companies have more powerful scanners standing by for purchase & use. It really becomes a question of how much is too much? And, for what benefit am I being dosed with an extra amount of radiation?
Unfortunately, most travelers are unaware that they are even being dosed with radiation by a scanner. No doubt, the TSA would like to keep that fact hidden.
And for basically no value-add, since it's the TSA.
All in all, I think the TSA is awful and would love them gone. At the very least there should be regulation on the max amount of radiation that is allowed by a machine (not sure if this exists).