Flight was overbooked significantly and there was a prolonged hassle of folks getting on the plane, finding no open seat, and then deplaning, then having airline staff come on to count heads, then folks getting back on and then back off again. Many unhappy customers with confirmed seats getting tossed off and getting treated rudely by airline staff as the process frayed nerves. The frayed nerves of the flight attendants continued to be evident after the flight took off (and we were in front and could hear them trash talking about specific passengers).