In the first modern wave of UAV's there were things like the General Atomics Predator drones. They are used mainly by the military and at first in surveillance only roles. Few know that a long ways back, under Clinton, Osama Bin Lauden himself was spotted by an unarmed drone...and the Executive Order was given to crash the aircraft into him in an attempt to kill him. Members of his party were killed, but not him. From that point on GA and others began to modify their existing airframes to carry weapons. GA moved into the Grim Reaper series, armed with Hellfire missiles as a result. These aircraft are larger than most Cessnas..to give some idea of size. From there, rules of engagement have taken over.
Quadcopters have been a recent advance, coming directly from the hobbyists world. Somewhere along the line, the tinfoil hat brigade decided they were all owned by the government/ police/ unknown black agency...and were being used to spy directly on them. R/C modelers are outraged over impending laws as a result of Quads being available wholesale pretty much everywhere. Photographers and movie folks are upset at these changes when they try and use them responsibly. To them they are simply a tool for getting the shot they want, they couldn't care less about drones, aviation or anything else. They are simply a flying ladder or camera mount.
As to shooting down something over your property....you don't own the air, the FAA does. Just like your property rarely comes with mineral and oil rights beneath it. Most of the people so afraid of having their pictures taken by "drones" have nothing worth taking pictures of. A friend of mine got sued by some nutcase woman for "stalking her and taking her picture" when on assignment to get photos of a beach for use on the county's website. A rather ugly woman in the first place, she was so very sure she was the only thing on the beach worth taking a photo of. Within my extended group of photographer friends, I know of a couple who have had their Quads shot at or down....and the resulting lawsuit was lost by the nut who shot them down. They were very unhappy to find that a professional Quad alone cost over $4000.00, the camera body was another $6500.00 and the lens was around $7500.00; not to mention attached charges for issues regarding use of a firearm. They might just have shot down an older Cessna for what it cost them.
Funny thing is, I know an aerial mapping company that has such a huge camera array that it requires a Cessna 182 to carry it...and they never have a problem flying low over anything.
