We all have windows - and many of those windows open. A basket that hangs outside the window with a battery powered beacon is another option for delivery. The baskets could even be secure and waterproof.
The issue I see with delivery to windows is all the clutter that is commonly found in front of windows such as power lines, tree branches etc. since that cannot yet be easily detected with computer vision and inexpensive 3D sensors.
This is what I would like. Even if they use a regular delivery truck most of the way, it would be great if they could cover the last fifty feet with a drone, to leave the package on my balcony.
(Amazon's switched to using their own courier service in my area. They make one delivery attempt only and won't leave packages at the door. So right now I can't use Amazon any more.)
Technically, this seems really hard, since GPS might not be enough---too much interference close to the building, trees. But maybe it is possible to get enough onboard visual processing to make it doable. Pretty interesting research problem.
GPS is most certainly not enough for navigation next to a building since you can hardly get an accuracy below 5m. I would bet on navigation by computer vision and 3D sensors.
Another interesting aspect of this is the choice of location where to drop the package. You certainly would not appreciate finding your emergency math textbook in the middle of your flower bed. This could for example be solved by setting up delivery spots in advance, or perhaps by using human judgement through something like Amazon's Mechanical Turk.
You'll just get your Amazon Prime Beacon™ which you just put on the floor and sends out little pulses to guide the drone.
But I doubt it's technically feasible.
1: These could deliver into my apartment on the nth floor by coming through an open window, as well as the mentioned balconies and front yards or the roof.
2: We could not just set our delivery point up using a app on our smartphones (GPS wtc), but those phones could also broadcast over the various radios to the device and even use the camera to help the UAV navigate. Enter a few hints about route and off we go.
3: The UAVs can be launched from delivery vans to save on the flight time from the larger depot. Drive to a delivery area, deliver the big parcels by hand while the little parcels are automatically delivered by UAVs operating from the roof of the van.
4: The cost of UAVs will come down - significantly - so they may become semi-disposable for the delivery company. In 2015 that may not be true, but by 2025 I can certainly see it.
5: The UAV's could, if they are set up with the right taxi-like business model, be used by a variety of delivery actors, including individuals as well as businesses. So after the Amazon delivery I use the drone to take a parcel to the post office for delivery to an eBay buyer.