Give someone a stick and he'll find a way to fuck someone up with it, by mistake or intentional. These things, here in the UK at least, are heading towards some form of control measure at light speed, it wouldn't surprise me if it was announced tomorrow. These are great fun and should be treated with respect and consideration for others.
Sadly anyone can buy them, a 10 year old who just got his xmas money from Santa could walk into a store tomorrow and walk out with a machine capable of insane amounts of tissue damage or worse. Another factor is that they're easy to fly, but hard to master. Anyone can get them up in the air, but if there's a gust of wind or things get dicey, control is lost way too easily, which results in crashes.
The biggest problem however is that there's no way of finding the pilot. I could rig one of these up today and fly it 10 miles away, if it crashed and caused harm or damage, there's no way the law could trace it back to me, which is a massive fail. Granted this goes for most RC but for some reason these drones seem to attract idiots by the boatload.
We've had two incidents in the UK already where someone has flown over and airport with them, one of these airports being Heathrow, one of the busiest airports in the world. Then there are the guys who fly them over stadiums when there's a match on. Yes it's fun, and cool, and blablabla, but it's immensely irresponsible. It takes one small gust of wind, one small component failure, one lapse of concentration and you could literally kill someone.
It's no joke, I do think that these things need regulation, some form of training and certification and perhaps a minimum age for unsupervised pilots, because as it is now, it's a wild west where anyone can do whatever they want with very little consequence, if any.