Well, I've flown model aircraft for many years. It requires skill to learn how to pilot these things and most clubs require you to have insurance in case of an accident. Now though, anyone with the money can purchase a drone and fly it pretty much wherever they wish. So the problems I foresee include accidents, privacy issues with the cameras they fly and unintended landings. Like I heard that there was a dead drone at the bottom of one of Yellowstone park's thermal pools.