I always tell my students that there is no such thing as a stupid question. And they don't ask stupid questions. They come prepared, which is to say that they ask questions that expand on or fill in gaps in the assigned readings. There is always something useful to the rest of the class embedded in every question. The worst experience I have with their questions is that sometimes they are ahead of the syllabus and I have to say, "Well, we're gonna address that, so hold that thought."
Then I attend a workshop with my peers and am reminded just how stupid a question can be. I went to one such event yesterday. About halfway through the morning a woman in back piped up with a request that we hold questions 'til the end: She was kinda concerned that everyone would be mad, but a bunch of us cheered.
So apparently I'm not the only one who was seething with impatience over the sheer stupidity of some psychologists. My graduate-school experience was similar in that there were always a few people in every class who were not prepared and would ask questions for which the answers were right there in the assigned reading! I wanted to scream sometimes.
Then there's always the one participant who isn't really asking a question, but who wants to argue with the presenter. Or the one who is actually just seizing an opportunity to show everyone else how knowledgeable they are on the subject at hand. They aren't actually asking questions either, but making speeches--sometimes quite long ones. Somebody oughtta do a study on inappropriate participant behavior. There's grant money in there somewhere, I'm sure.
Yesterday's experience also reminded me about the importance of crowd control. People who present a couple of workshops a year do not learn how to manage a classroom, and yesterday's expert was no exception. As an adjunct I had to learn pretty quick. It's not pretty: Sometimes I resort to yelling, "HEY!" in my command voice. But it gets the job done.