Is Amazon's Drone a Practical Idea?

http://money.cnn.com/2013/12/01/technology/amazon-drone-delivery/index.html

http://www.cnn.com/2013/12/02/tech/innovation/amazon-drones-questions/

Many of us might hear the rumor of that Amazon is developing drone helicopter to deliver their package. According these recent news articles, it seems that there is almost no technological issues of making this sci-fi idea real. Amazon is making a great effort to try to get FAA amend their regulation to allow the deliver drone legal in commercial use. However, there are some issues still look problematic, and some of them even look a little funny.

How would Amazon prevent people to steal packages on drone and drone itself? It seems one of the obvious advantage of using drone is to avoid the cost of using labor. If no one is watching the drone, how could Amazon ensure this small thing is safe on its tour?

How would Amazon ensure the delivery? In the big cities, the urban planning is usually very complicated. Given the drone will find the correct address of an apartment, what is the next? Leaving packages on the front door is generally not a good idea especially in big cities. It is hard to image how could a drone ring the bell.

How about avoiding random obstacles, specifically small obstacles like wire, or even a moving bird? It is unknown that if this aspect is in consideration of the drone design.