It's happening
At a recent sanctioned cross country motor cycle competition (NSW) an individual turned up with a quadcopter/camera. One parent of a junior competitor objected to its presence on the grounds of infringement of privacy. Given the fact that there were umpteen other people photographing the event conventionally this was rejected. The operator of the UAV told organisers he could fly it however he liked including to over 1 km altitude.
During the course of his activity, he lost control of the device & crashed it into a competitor waiting to start a race on the start line. Fortunately, of course the rider was wearing a crash helmet & no injury was sustained, although the UAV was seriously damaged.
I believe the organisers are implementing a ban on UAV's at future events.