As s.petry points out, YMMV. I have a prosthetic hip and various other bits of ferromagnetic material embedded inside me. That triggers said metal detectors. That means I get patted down. Every. Damned. Time.* And I fly a lot. I'm on a first name basis with a number of TSA agents at our (small, rural) airport.
While it doesn't trigger PTSD or other major psychological pain, it's is annoying to have some stranger ram their hand up their crotch in full view of everyone else. I've been delayed in larger airports who haven't seen me before (or whatever). No, it's not necessary.
*And, for some random reason (perhaps because I haven't blown up a plane yet AND have a TSA supplied airport pass) I have been on the 'prescreened' fast track for the past couple of months. Shoes on, the metal detector must be turned off or it's not a standard detector because it doesn't even blip. But sometimes I'm not on the fasttrack, maybe I said something on my cell phone or on Slashdot or perhaps it's just random (although that is approaching being smart about it).
So not painless, not necessarily minor and the paranoid lunatic fringe here has amply documented excesses, lapses and generally nonsensical behavior on behalf of the TSA. And don't get me started about the back end of the system. If you saw who could wander around unmolested inside the plane at most airports and if you saw the processes whereby these folks were 'screened', you would wonder just what they're trying to accomplish.
The scary bit is that the paranoids aren't paranoid enough. No, we aren't Communist East Germany. We're not Russia or China or any other of the many less fortunate places. But we're trying to get there. And when Americans put there mind to it, there isn't anything we can't screw up better than anybody else.