Saying "good question" during a seminar talk During seminars and talks, some presenters hear a question and compliment it by saying "Good question." Could this possibly offend the asker? Could this be viewed as a tactic to pretend being unfazed by a difficult question? 

Or is it really a good psychological ploy to mollify the interrogator so that he/she is more accepting to the answer?
As an economist I can rant for hours about people's ulterior motives... as a speaker I can tell you that this reaction springs in me spontaneously, when the question has good timing with what I am presenting, meaning that it is a good opening for the next issue (or next aspect of the current issue) I was about to start speaking on. It makes a presentation rolling with the audience, and you cannot ask much more than that.