My own experience of High School showed me teachers were a mixed bag - some excellent, some very average and some very lazy. Occasionally good teachers had bad moments.
I've got mixed feelings about YouTube's 7 Scariest Teachers, a selection of teacher rants caught by students with mobile (cell) phone cameras. Should teachers, who are already struggling to teach unmotivated students, be exposed to public ridicule like this? On the other hand this could help weed out people who shouldn't be teaching.