Seems more likely to happen in China than in the US
We'll see self driving cars before we see autonomous drones delivering packages to our houses. Amazon has pockets way too deep to not get sued for 7 or 8 digits every time one of them has an issue (whether a malfunction or someone hitting them with a BB gun or green laser pointer or whatever) and goes down on someone's head. Or goes down near someone and they make it look like it went down on their head, hoping for a payday.
I can see a new sport arising: "guess which drone is carrying an iPhone [or other suitably expensive and easy to resell item]" Send up your own remote controlled chopper and drop a net onto the Amazon chopper, which tangles up the blades and causes it to go down. Presto, one free iPhone!
I give Bezos credit for thinking outside the box, but just because someone wants to try something new on a big scale doesn't mean that his solution doesn't have too many problems to be workable. Yeah yeah, someone will say "obviously they've thought of these problems" and I know they have. They think they can overcome them, but they underestimate the sue-happy culture in the US, and people liking to screw with "the man".
Yes, Amazon is just another big faceless corporation now, it is just as much "the man" to average people as IBM was 35 years ago or Microsoft 15 years ago. I doubt Bezos thinks of himself as "the man", but when you're trying to take over all of retail you can't escape it. He wants Amazon to be Buy-N-Large from Wall-E, you don't more "the man" than that!