I am seeing a lot of people talking about how easy it would be for a kid to grab a bb gun and shoot one of these down. I really doubt that. I mean, hitting a moving airborne target is not easy. A bb gun, even if it could do enough damage to the drone to crash it, is likely not accurate enough over a distance to hit the drone. It would take at least a .22 to have even a tiny ghost of a chance to actually hit it, and there we are getting into actual firearms. And despite what people tend to think about gun owners they don't just fire their guns into the air for the hell of it. That is extremely dangerous and will get you jail time.
Not to mention the fact that the thing will wiz by in seconds. You would probably have to be waiting, gun loaded and ready, actively scanning the skys, to even get a single shot off. And most areas will only see one or two deliveries a day, if that, for a large neighborhood. About the only time the thing will be vulnerable is during the landing and take off parts of the trip, which means a kid will have to be ready with his projectile and just so happen to be in exactly the right place at exactly the right time.
And you can bet that the first time this does happen Amazon and the government are going to come down hard on whoever did it. Property destruction and public endangerment are not light charges. People are not going to risk jail time to shoot down a robot postman and you can bet that parents will teach their kids not to do it because it will be the parents that take the flak if their kids are morons.
Frankly, while there are many problems to be solved, kids with potato guns are not a big one.
I mean, you will probably have one get shot down every once in a while, but no where near often enough to make a slight dent in amount of money Amazon could make on this.