[TeMPOraL]

Over streets is one of the least safe place to fly - imagine a 10km brick falling at 40km/h into incoming traffic or a group of pedestrians. As for the final contact, your average quadcopter will have like 10-20 minutes of flight time tops; it can't just wait for you to signal it - being even a minute late could mean the drone won't make it back to a charging station.

[JoeAltmaier]

Very true today. Batteries will get better, or maybe metal-air with huge capacity. OR, it could deploy a balloon and wait for the signal :)