I was coming back from Europe a couple of years ago through Atlanta's Customs.
We all had to stand in this long line and go through security again.....AFTER claiming our luggage, going through Customs, and rechecking our luggage.
There was a couple(American) behind me, bitching no end....and loudly.
I went through first, got pulled over to be searched/wanded...
They went through while I was waiting....and were taken away.
I asked why I was being checked when I had already gone through security and Germany....I was told it was because foreign countries' security checks are not as thorough as ours and because we were being "released" into the secure side of Hartfield.
Also asked why the couple was taken away....and was told, when someone bitches a lot....or appears "frantic"...it puts Customs on "alert".
Never ever make smart remarks to a Customs/TSA person....