In cities it seems like a good idea. Millions of customers are within drone range in Manhattan. Drop packages on a building's roof, a doorman brings them down to the front desk, there you go. It can take several hours to drive a delivery across Manhattan at rush hour.

As for the range, electric cars mean that batteries are receiving a lot more development and economies of scale, plus people have been working on package switching networks for years already now.

Is it going to happen tomorrow? No. But Walmart can afford to be in it for the long haul.