Unfortunately, learning psychology suggest that the learning process in hedonistic. One learns most what they engage in. By asking questions, going to hypos, etc. one maximizes their learning. For the rest of the class it really sucks however. They way I see it is if the rest of the class is not asking questions, and the prof asks for comments, why not speak. If a student talks too much then its the prof's fault for calling on them or the class's fault for not talking themselves.