AMZN can allow itself to implement infrastructure/process to use something like Al metal-air cells. Stick in, stick out, sent resulting Al oxide to re-processing. You'll get efficiency and range of at least gas engine without mess/maintenance. There are more advanced schemas available (like potassium based - more energy dense, easier for reprocessing), unfortunately most of the money is in Li based schemas which would make sense only if Li were to be the main by weight component, which isn't going to happen in any near future.

>Wide use of overhead power lines in cities makes drone delivery unsafe in cities.

that just control/sensor problem, pure tech and very solvable issue.

>I feel this is somewhat misguided

we need to utilize 3D en-mass, in particular for transportation. Whatever industry starts it doesn't really matter in big picture ... End result anyway will be an autonomous octocopter for commute :) (the autonomous cars Google develops will be great for trucks which will roam roads empty of people carrying cars)

I guess at least companies are dreaming again and trying crazy ideas, aka "moonshots".

Sitting on "moonshot" sized piles of cash and having engineering pools of that scale, one can expect that at least some would try ... I mean actual placement of Amazon logo on the Moon (like say using 100 "dots" - very bright LED array panels) would cost only something like few billion dollars.

Stringing taut wires is also hard and they are more susceptible to damage which require constant fixing (see Connecticut ~4 years ago).

Gas engines are heavy, compared to electric motors and lithium batteries, so for modest endurance flights, electric works out better now, but for long endurance flights gas or diesel would be better.

Curtis youngblood demo'd a nitromethane powered quad as seen here

http://diydrones.com/profiles/blogs/curtis-youngblood-single...

I can't imagine anyone would use a nitro powered platform for any commercial use, the fuel is too expensive and the motors require too much maintenance.