We were there Dec. 15 - 22 and they were rolling out the random screening for the detectors, but we didn't know it.
My son and I were going through the no bags area while the rest of our party queued up for bag check. One guy in a "Special Events" vest asked my son to step over, not explaining ANYTHING -- he looked like he was signing people up for cell phones, certainly not security.
My son, 23, who is quite large and bearded, smiled at him and said, "No thank you!" and kept walking. It was only later that we clicked to the fact that he was being asked to go through additional screening!
And the guy's reaction didn't tip us off either. He just smiled back and said something like, "well next time I might have to make you" but it was in a joking manner and we just nodded and laughed, still under the impression we were avoiding a sales pitch.