Power lines, objects like cars and people and pets on the ground, pools - I wonder how these things will avoid doing damage. Frankly I would be pissed if they drop things on my head or my car.
Finding a clear drop point is easy (lawns, for example), and the drone can sound some alarm to let pedestrians know its landing.
That would make the "where to land" and "how to drop the payload" much easier.
This is the future, the limiting factory is battery tech and aerodynamic drone design (which is a key problem with quadcopters - they are incredibly inefficient; you need wings during level flight for efficient operation).
... and regulation. :P