A 1-2ft wide target moving at 45mph 400' above you? (so unless it's -directly- overhead it's actually quite a bit further away than that) I don't actually know of that many people who are willing to risk shooting a rifle into the air in a populated area, anyhow.

In fact, I'd be willing to say about 1% of people will be in the top 1%

The only real issues with eventually getting this to work (assuming they'd be flying in the 300-400ft altitude that is currently legal airspace for hobbyist RC flyers, the max altitude tends to vary based on how close you are to an airport) are running into birds and running into -other- drones. The second could be solved with a standard broadcasting signal similar to what jet aircraft use to notify each other of their position. The birds... well, they need to learn to get outta the way! (really a proper sensor array could detect obstacles and dodge them, multi-rotor aircraft can change direction -quickly-, my quad will go from 30mph to zero before I can say 'shit!' because I dropped the controller)

For most of the drone's flight, it would be well out of range of any but the best marksmen, and do the best marksmen really sit in their back yard looking for something flying 400' overhead to shoot at? That's moving at 30-60mph?

For folks worrying about high winds, I suggest you find somebody that owns an octocopter and check out how stable they actually are. It would take a decent storm to knock them down, and the simple solution is: no deliveries during storms. My dinky quadcopter can hover in place in 20mph winds(not that I'd want to -fly- it anywhere in 20mph winds, but it can hover!), a heavier and more powerful octo capable of delivering 5lb payloads could handle substantially more.

Not saying this isn't just an attempt at publicity for amazon, just saying it's not out of the realm of possibility. If another hobbyist RC flyer would like to offer a counter opinion, go ahead. :)

Lots of people privately own quad/hexa/octo copters, some of which do some pretty spectacular things autonomously. We even have a club in my town for owners/builders. A guy I work with has a GPS on board that he can use to pre-set coordinates (he can use the same GPS for either his quadcopter or his RC airplane - he actually just takes out the whole ardudrone assembly and transfers it between the two) that the drone will then fly to and return to its home position at the end. I think he said the total cost for his quadcopter came in around $500.

Avengers flying fortress aside(which somehow needed -two- engines to fail to go out of control), things aren't pretty when an engine fails on a quadcopter (ask my AR.Drone). 'Course, Amazon is proposing octocopters, which can suffer a number of engine failures without the thing losing control(unless you lose 2 engines on one side). Luckily making an octo is as simple as hooking up two engines to each output of a quad controller, the controller will generally compensate for lifting power differences when an engine fails.

Who are 'most people'? How many households do you know of that don't own a desktop or laptop, but have smartphones?

But what will I do with the 600 or so micro USB cables I currently own?

Don't forget solar chargers for low-powered usb devices are in the ~$40 range, last I checked, in case you want to take your whole library on a cross-country camping trip or whatever. :)

Joke's on you, you got a frontlight! :P

Personally I read my books on 4 different devices... a laptop, galaxy s2, nexus 7, and a kindle paperwhite. It's very rare I'm not within 10ft of one of these.

Only problem with keeping them in a car is they tend to be alive. If you're going to use reusable bags, please wash them. BTW, what the heck happened to paper bags? Those decompose pretty quick.

Does a TV tray next to my comptuer desk count?

:P