Not negativity for the sake of negativity. While the link I posted is a large single rotor helicopter, I was trying to show a worst case scenario. If Amazon Air does get off the ground then I would imagine the program expanding to delivering heavier packages over time, which would require larger quad copters and thus larger rotors and higher risk of more serious injuries.

I have built and fly hobby planes and copters in my spare time. They are dangerous. Once, after one of my planes crashed near me, I picked it up without giving it a second thought and sliced my hand wide open on the still spinning front propeller.

I don't necessarily believe this is a technology that will result in fatalities, but certainly injuries, especially to children and animals.

On a less dangerous note; I fully expect some shenanigans from people shooting these things down to get free goods.