I did it on my last Circuit Assembly talks, back in 2005. I was still a Bethelite and was there as the "Branch representative". I only did it in a covert way, but still understandable if you listened (even contradicting the talk given by the Circuit Oversee, who I considered an asshole). I used Bible verses to say exactly the opposite of what the CO said. During the talk I was calm and vigorous (even having to stop myself to become too bold). Then I finished and my knees went weak and I was literally trembling. The DO called me into his office, I thought he would pull the trigger. To my surprise he was all laughs and happiness (had 3 pretty, single sisters there "serving" the Assembly Administration - laughing, talking and serving him Coffees - and god knows what else).
He said that I was a bit overtime and asked me one or two things about Bethel. He had the outline in front of him, but was clearly NOT paying attention. As I was "prominent" and from the Branch, he might have thought that this was some kind of "advanced light".
Later during lunch time only ONE ministerial servant approached me (he was new in "the truth" and freshly appointed) and asked me if I was absolutely sure of the points mentioned in the talk, as they seemed to contradict other lines of thought of the assembly. He wasn't even one of these "ubber-witnesses", a pretty relaxed, laid back guy, married with 2 younger sons. Also not the sharpest "Bible scholar" out there. He really surprised me for taking real attention and having the guts to approach me.
This was ONE GUY out of an attendance of approx. 2.500. It made me wonder if the others where just sleeping or so brainwashed that they would lap everything up that would come from "someone from the Branch" or the GB.
That was my last time on stage. The following month I left Bethel, the assignment (this was in a foreign country) and gave all my "privileges" up. It was one of the many, many proofs that showed me: no holy spirit around. I could have announced that everybody should strip naked and they would have done so.