I seem to beep quite often (not sure why - it could be my watch), so I get pat downs quite often. I haven't been groped for quite some time (I have got really groped by a security screener many years ago) and I would prefer to be patted down, rather than take the unknown risk of the body scanner.
I have had more than my fair share of radiation since when I was very young due to injuries etc (literally dozens of CTs, X-rays, fluoroscope etc), and I also fly rather a lot (100+ sectors a year). I will also need a lot of X-rays and scans in the future as I am at a very high risk of osteoporosis and have a condition that needs monitoring through scans. So I would really like to minimise my unnecessary exposure to any form of radiation, microwave energy etc. So, I'd take a pat down any time, despite having been groped.
In addition, I would prefer to see who is looking at me. If there is a one-way mirror where I can see the screener but the screener can't see me, the body scanner is somewhat less unacceptable (except for the reasons above).
Besides, I also believe that a body scanner will merely drive any determined terrorists to conceal the explosives in their body cavity. What next? Compulsory colonoscopy and colposcopy before flying?!
I feel that it would be much more wise to deploy explosives detector. They are pretty non-invasive and not as much a risk to privacy, and probably more effective.