I always opt-out. All you have to do is walk up to the guy directing you through either the metal detector or the backscatter machine and say "I opt out". Yes, they will give you an intensive pat down but it is much more awkward for them. Being cheerful, smiling, and making jokes whenever they explain what they're going to do next is the best part of it as they get a martyred look on their faces and grimace. Almost all of the TSA floor agents are minimum wage low education individuals(here in Atlanta it's the biggest employer of people on parole/probation) who have a few days of training at best.
Even if you don't like being touched, opting out is the best way to get the scanners removed entirely. The TSA is currently in violation of the DC Circuit Court(and has been for 2 years now) about removing the scanners, the more people who opt-out and take the longer more intensive pat down, the slower security is and if it gets to the point(I think the numbers were like 1% of flyers opting out) it would bring security to a complete gridlock and force them to remove the scanners or start causing everyone to miss their flights.