The part I'm I think will be the big show-stopper is the likelihood of people 'catching goodies from the sky'. Given the technical restrictions of these drones it seems fair to assume they'll be used mostly for 'small but expensive' goods. What's to stop people from building a microwave-gun to fry the electronics and run of with the cargo ? Heck, a decent slingshot could probably bring them down. I realize one could rob any courier service, but with drones it's going to be dead-simple unless they start building in all kinds of security measures but thus limiting the capacity/range/... of the machine.
Yes, I was thinking "shotgun", but your ideas are better. Let's run with it a bit. How about a good old fashioned barrage balloon? Or use it to loft a fishing net, or why not a kite? "Honest officer, here I was just flying my kite, minding my own business and all these drones started to fall all around me, not my fault really..."
Or, for the ultimate thrill. Your own drone/RPV. There have been "dog fighting" competitions between RC-planes for ages, trying to cut someone else's streamer with your propeller. Now you could actually make that game worth your time.
Then there's good old fashioned GPS-spoofing that can be done for cheap. Make the drone land/drop thinking it has reached its destination? It's manna from heaven all over again, only this time courtesy of Amazon...