Last year, as the quadcopter fad took off (ahem), Amazon made a fun little video of an Amazon-branded quad that delivering a tool to someone’s home in 30 minutes. It was a joke. Yes, Jeff Bezos has created and built Blue Origin, but that’s a very different thing than RC toys delivering packages. Seriously – IT WAS A JOKE.
WHY was/is it a joke? As an RC helicopter “pilot”, I can give you several good reasons why small product delivery via any unmanned aerial vehicle won’t happen in the next many years.
Weight
The inexpensive quads (let’s say ‘inexpensive’ has the ridiculous definition of $500) can’t carry much payload. About 12 ounces. A single DVD and case weighs about 5oz. So if you’re ordering two DVDs, maybe you’re okay… but forget it if you need powered sugar (16oz) for that frosting or you have a craving for Oreos (15oz).
Battery and distance
As of 2015, the batteries that run RC helicopters just aren’t that good. Even the newest tech batteries and heli’s get 20 minutes of flight time at most. Well, unless you are flying a monster helicopter that can carry some big batteries – but that also means less payload. And what about distance? At a max speed of about 35mph – which also means you’re draining the battery at top-speed – you better live close by a distribution center. That means at most 10 miles away – because it needs to do the round trip, plus carry a payload. Plus takeoff, which drains the battery more than sustained flight.
Capture
People would LOVE figuring out ways to ‘capture’ these pricey little toys. The first thing that comes to mind is a DIY net gun. Ya know, an air-gun that shoots a net with a small weight on each corner that you can fire pretty far. 
Amazon’s quads would be like a fly in web. So no only would the inventive kid and his net catch a cool piece of technology that they could dismantle and re-use, they might get a couple DVDs or a cool 3-sided wrench.
Heck, forget about something as physical as a net-gun… there’s RF jamming hardware you can easily build that can cause RC toys to run amok. Oh, and don’t forget about rocks. Rocks are pretty… free… and kids love to throw rocks. One good hit and that 30 minute delivery never shows up – and Amazon just lost a $500 toy.
Obstacles
Now, probably the biggest issue is obstacles. I’m talking about power lines, low-hanging tree branches, water sprinklers, dogs, patio furniture, street lights… and people. Even the most sophisticated drone helicopters can’t navigate those items with much surety. I’ve had dogs chase my quads and REALY want to eat them, if they could only get their teeth into them. And yes, I’ve even hit light poles when I thought I was far enough away. Sure, there are good cameras and sensors you can add to copter, but every ounce added means shorter battery life and a smaller payload. Then, let’s not forget about good ‘ol human stupidity. The moron who wants to get a little to close while the device is landing and YOW! Those blades WILL cut you, and good!
So, if Amazon can work through all of the items above and still make it cost effective, then sure, you might see Amazon Air 30 minute delivery – if you live in the parking lot across from a distribution center.