[Mountain_Skies]

They're unmanned though there could be a danger to people on the ground if there was enough damage done that it couldn't land under control.

[squarefoot]

Also if the idiots know they're unmanned and used to deliver goods, they could be even more motivated to attempt to shoot them down to steal the cargo. I also would consider putting cameras and the necessary technology to help identifying anyone attempting to shoot them down.

Or maybe paint them as sharks, then add some powerful lasers on their back:)