Traditional RC aircraft are extremely niche. They're expensive and hard to fly, so you need some dedication to get into that.

Quadcopters, on the other hand, can be purchased for $40 and flown by somebody with no experience. Obviously a $40 quadcopter won't be threatening airliners, but it's representative of a big change all over the spectrum.

I flew RC planes in the late 80s when I was around 14. There was a barrier to entry back then. It wasn't money, although that was part of it. You generally had to build the planes (much more involved than assembling a ready-to-go drone), and then learn how to fly them. The were not easy to fly like the current drones are. Part of the training we got was not to do stupid stuff like fly around airports. Those barriers to entry are gone, so now you plop down $1000 or less, and a day later you're up and flying.

A large part of it is their ability to keep themselves stable. That opens up a huge range of uses that weren't there previously, as well as reducing the chance you'll break it the first time out flying it.

I was thinking about this recently; seems like affordable consumer quadcopters are a consequence of the availability of cheap, lightweight solid-state accelerometers. Why are accelerometer chips cheap? Because they're ubiquitous in phones. Why are they ubiquitous in phones? Because Steve Jobs wanted the original iPhone to be able to tell which way up you were holding it.

(also, due credit to laptop hard drive 'freefall sensors' as another contributor).

Combine that with the cheap lithium battery and digital radio communication chipsets, also driven by phone volumes, and that's why 'radio controlled helicopters' are no longer a niche hobby, and instead a danger to aviation.

Chris Anderson talks a lot about the smartphone-drone connection here: "How I Accidentally Kickstarted the Domestic Drone Boom" http://www.wired.com/2012/06/ff_drones/

Don't forget the ultimate technological crosstie here: Using the phone as a controller for the drone.

Because quadcopters are very easy to fly compared to either fixed-wing RC planes or RC helicopters with the traditional rotor arrangement, and the price of the technology has been in free-fall. And quadcopters are a relatively new thing; Affordable ones have only been on the market for a few years.

A $500 dollar drone (or a $200 home built arduinopilot drone) can follow a GPS flight path and return to a fixed point with no input from a pilot. They are autonomous.

The ease-of-use of these modern "radio-controlled aircraft" is unprecedented - vertical takeoff, live video, intuitive controls - making them much more pervasive than ever before. That's why they're getting more mindshare - AND getting into more trouble.

Quadcopters with a GoPro attached are useful in a way that r/c planes never were.

It's because they're more popular now. That's it.