I used to do Ashtanga, a self led practice, in a group setting. In this kind of practice, you go at your own pace, everyone learning the routine at their own pace. People at varying levels would all practice together, so inevitably, there would be someone in headstand or in handstand, in the middle of the room, which was completely crowded, each mat inches from the next. If you fell, you might take down 20 people. I never saw that happen.