There's a reason why it's taking so long for Amazon to get FAA approval for drone delivery and this is exactly why. There are people in important places asking these sorts of questions already.

My guess personally, is that drone delivery will ultimately just be a tool for a self driving truck to get the package from the truck to the door. Drones are not nearly good enough as it stands today to do end to end deliveries at an industrial scale outside of maybe a few rural areas.