Usually the rule is "uninvolved persons" and it's meant to protect the public at events and parks, etc. If you are filming a car driving on an out of the way road where everybody is involved, that's not likely to be an issue. A kid in the garden with their parents supervising is not a problem. Flying over people trying to have a nice picnic at the park that you don't know is a problem.
Type "Drone fail" into YouTube and dive in for lots of accidents. The one that always stands out for me is a very large commercial drone that impacts millimeters behind a skier on a downhill racing course. "Crash" would be an insufficient description. It burst into pieces and made a small crater. If it had come down on the spectators, it was big enough that it could have killed somebody or caused very serious injuries. Another good one is a very bad operator flying one from the balcony of a skyscraper in New York until he smashed into the side of one too many buildings and his drone dropped many stories and landed pretty close to somebody on the pavement who scooped it up and sold the footage to the local TV news station. I don't think the owner was going to be too keen about retrieving his property or claiming Copyright on the video.
Biting the hand that feeds IT
