Pre-arranged filming risks:-
a) Pilot pushing the limits "showing off" to the camera
b) Cameraman divorced from reality/sense of danger because he's seeing it happening through a viewfinder.
The famous "f*** me, f*** me" video of a well known presenter being surprised by a very low flying Spitfire is a great laugh, but illustrates the problem. The margins were not great and the cameraman didn't even duck.