Will spotting Amazon's fleet of "Prime Air" drones soon be "as normal as seeing mail trucks on the road today"? That's what Amazon is saying, after CEO Jeff Bezos explained Sunday that the company would, in the future, deliver packages by quadcopter. However, that future may be a bit further out than the revolutionary retailer can say.

Coming from a company that employs robots in its warehouses, the drone vision isn't too surprising. And sure, delivery drones are already a reality: The Marine Corps have been using two remote-controlled K-MAX helicopters to deliver supplies in Afghanistan. It was so successful that the military extended their deployment indefinitely in 2011.

But while they may be welcome in countries with little or no infrastructure, delivery drones flying through tightly regulated skies over the world's biggest cities present a logistical nightmare, and are, to date, mostly wishful thinking. Newspaper delivery drones in France? A prank. Pizza delivery by Domino’s drones? A PR gimmick. TacoCopter? A hoax. The drone that tried to deliver contraband into a Georgia prison? Busted.

"A quadcopter airlifting you the next iteration of '50 Shades of Grey,'" is "going to be a gimmick” at least "for the next five years," Drunken Predator Drone, the persona behind the parody Twitter account @DrunkenPredator, wrote to NBC News in a surprisingly lucid email.