From Yahoo News:
Rep. Harry Mitchell, D-Ariz., viewed the machine in use at the airport Friday and said privacy concerns have been addressed because the screening is voluntary.
"It does provide a higher level of security," Mitchell said. "Hopefully it will speed the process up. The fact is that we want to be efficient.

I wonder if Rep. Mitchell would be saying the same thing if a TSA agent was looking at the image of his wife or mother.