If you find yourself asking more than one question per lecture, examine your motives. It is, I suppose, possible that they only began to ask such questions after they became distinguished, but I believe that a willingness to ask when they do not know is a characteristic of many great minds 5 . The ancient Greeks attributed the following saying to Euclid among others. Ptolomey, King of Egypt, asked Euclid to teach him geometry. Mathematics is hard, there are no easy ways to understanding but the lecture, properly used, is the easiest way that I know.
Television allows channel hopping and conversation.
At public performances, private conversation, however interesting to the participants, distracts the rest of the audience from the matter in hand. It must be added that just as good eaters make good cooks so good audiences make for good lectures. A lecturer will give a better lecture to a quiet and attentive audience than to a noisy and inattentive one. In the past some universities made lectures compulsory. In Cambridge during the early 19th century attendance at lectures was not compulsory but attendance at Chapel was.