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.
Solution: every 17th drone is a decoy carrying a paint bomb to mark anyone who robs it or were just standing around not trying to defend it or defending it effectively enough. Then the Amazon corporate police can swoop in and deal with anyone with paint on them.