As I've seen this implemented, the teachers know if the students played the videos or not. So the teachers can make a judgement call about helping the kids who didn't view them or answering questions for those that did. Unless you're waiting for a question to be answered, there's no reason to proceed slowly. I don't know why you are implying that some students will expect others to do their work for them, or how that would be specific to flipped classrooms.
The teachers have no such discretion, unless they've decided they want a career change. Otherwise, NCLB and testing-based teacher assessments pretty much demand that the teachers waste all their time propping up those who failed to do the required viewing.
