I agree that it is a great idea but it would require a huge amount of legislation change from the FAA - that's what held up the initial plans from the likes of Amazon and the beer company last year.

The concessions that the FAA have granted so far for utility inspections require the use of a qualified pilot, or somebody who has undergone specific training for drone flying, and that the drone remains in the operator's field of view at all times. Obviously the latter would not be compatible with deliveries.

I certainly believe that suitable regulations will be drawn up eventually to deconflict aircraft and drone flights by limiting altitudes (to perhaps 2-storey building height), having exclusion zones on and around airfields, and mandating the use of conspicuity devices such as strobe lights.

In the meantime, I expect both the FAA and drone manufacturers will concentrate on the easier regulation problems to solve which relate to non-commercial use for military, law enforcement and survey / inspection applications within the field of view of the operator.