You be surprised =)
People steal construction equipments and bulldozers and other silliness all the time, and pretty sure that they won't have the licenses for it. Nothing stops some silly teenagers or insane guy from having a "chance of a lifetime" stealing a helicopter. For, they'll just have fun destroying it with a hammer or something.
...unless you're Batman, then you can put a simple cover on a huge flying vehicle on the top of a skyscraper for half a year in times of complete anarchy, and it'll be completely safe.