A Kentucky man shot down a drone with a video camera that was hovering in his back yard. He was arrested. There is an interesting discussion into the legalities of the issue here: Shooting Down Drones. It is well worth the read.
I might add that in a lot of areas it would matter a lot where you are at. In almost every municipality in North Carolina, it is illegal to discharge firearms within town limits. The argument would have to be that the drone "threatened" the home owner, but that is a little hard to argue if it is just hovering. Yves at Naked Capitalism I think was onto one method: "they need a magnetic pulse to fry these buggers."