Only one item can be delivered at a time. It can’t weigh more than 5 pounds. It can’t be too big. It can’t be something breakable, since the drone drops it from 12 feet. The drones can’t fly when it is too hot or too windy or too rainy.
You need to be home to put out the landing target and to make sure that a porch pirate doesn’t make off with your item or that it doesn’t roll into the street (which happened once to Lord and Silverman). But your car can’t be in the driveway. Letting the drone land in the backyard would avoid some of these problems, but not if there are trees.
Amazon has also warned customers that drone delivery is unavailable during periods of high demand for drone delivery.
I mean, the most obvious sinister application for this tech I can think of would be military dones that precisely drop small bombs on targets, but based on the ongoing war in Ukraine, that technology already has been developed, so Amazon of all companies developing it again would be pointless.
EDIT: come to think of it though, while the technology for that military application already exists, having a delivery drone industry might be a benefit to a country in wartime anyway, because the factories to build those drones could be repurposed to make military drones, and the drone fleet itself could be requisitioned, sort of like how navies have often throughout history pressed civilian ships into service in various roles, and with probably minimal modifications be used to gain a sizable fleet of bombing drones very quickly without having to have the military maintain that fleet idle in peacetime. Not sure this actually benefits the company much though, just the country that has a sizable network of these drones and/or factories to build them within it’s control.