When I teach, I sometimes feel like I'm talking to an empty room. An empty room full of 100 students. I'm not sure if students are just conditioned to be passive or if I lull them to sleep, but it can be very difficult to get them to give any feedback.
I feel bad. You'd think a decent teacher (and I consider myself slightly better than mediocre) would be able to keep students engaged, but I've seen students fall asleep in even the most dynamic lectures. To cope with this, I've decided to just amuse myself while I'm talking. If students aren't going to be responsive to the material I'm teaching, at least I'll keep myself amused.