I hate the TSA. Monumental waste of time, money, and rights violations galore.
Having said that, I always opt out of going through the x-ray scanners for 2 reasons. 1st, the radiation emitted is higher than your home microwave, and you wouldn't nuke yourself on purpose at home, right? 2nd, the ONE time I did go through the xray, my piercings suddenly felt "funny". Don't really know how to describe it, but it was enough to make me never want to go through one of those things again. Upon exiting, they kinda stopped me but didn't really do anything. The small TV monitor had a picture of a person and circles where all my piercings were. Then they just shooed me on through.
But when I opt out, and they're patting me down, they *ALWAYS* bump up against my PA. Next thing I know, they're purposely making a few more passes to determine what it is. One time, the guy did this a little too much so I just asked him if he'd like me to take it out and show him. He hurried me on through.
Otherwise, it never sets off metal detectors or anything else.