I have been on flights that had us all taking out our IDs to hand over with boarding passes...not many though.
I have also been at the gate several times, in recent years, when they did random bag checks as people were in line to board. They set up some kind of table and pulled random people out of lines. There were usually state troopers with them (TSA) when they did this though.
Theatre? Perhaps....most likely really. But, it just doesn't bother me as much as it does others. I do wish I could fly with full sized bottles of shampoo and such in my carryon bag again. But, until that is no longer the case, I will fly with airlines that allow me one free checked bag.