Regarding concussion: this is dangerously wrong. To be knocked unconscious due to a head blow is by definition a Grade II concussion. The emerging consensus on brain injury is that even lesser concussions can have severe long term effects, especially additively (see e.g. NFL and NHL brain injury scandals).

No one needs a lawsuit. It's all about taking responsibility for your actions. Getting knocked unconscious is pretty serious.

This is the important thing - if this had been a badly kicked soccer ball that'd bounced off a building and hit someone in the head and knocked them down - what would the appropriate behaviour and response be?

You own up - apologise - and accept responsibility. The guy here should have done the same, this shouldn't be about "drones", it should be about not being a jerk and a coward.

"The drone is 2 lbs."

I'm failing to see your point here. Ever been on the receiving end of a baseball? Much lighter than a 2 lb drone, but I sure as poop don't wanna be hit with one.

What do you propose to be the lower limit where we should start worrying about the weight of something falling from the sky? And having established that, can we arrange for a time to meet up so I can drop something that's just a little lighter than that amount onto your head from a great height?

A rotor blade can potentially cut or blind people.

Sure, but to be fair - a bicycle, a skateboard, or a baseball are also all quite capable of inflicting serious injuries.

We as a society seem to be perfectly happy to assume the risks of children on bicycles - and allow then to use them in fairly uncontrolled fashions in pubic places - and that all works out fine. We handle motorcycles differently - and at least where I am are working out the sensible restrictions for "in between" categories - bicycles with more or less powerful electric or gas motors.

I find the "drone hysteria" annoying - in that it's manufacturing unreasonable "generalised risks" (like "cutting or blinding people") - without acknowledging the difference between a Clarkson CX10, a Parrot AR Drone, a 250 class quad, and a machine capable of lifting several pounds or more of payload. It's almost like trying to apply the same risks and restrictions on 18wheeler trucks, cars, and matchbox toys.

I don't really disagree with you but there are probably certain activities that we can generalize to a pretty wide of drones as being unsafe such as flying over a crowd of people. Just as we tend to have (albeit often informal and not always followed) rules around bicycles, skateboard, and baseballs. Those are all probably fine in most empty parking lots. Probably less so on a crowded city sidewalk.

The thing is - I suspect there are three or so orders of magnitude more of this style of quadcopter:

https://www.dropbox.com/s/ybtq960nzf8dxl3/Clarkson%20CX10X.j...

Than the sort that'd have any real risk of knocking you out of they fell on you.

I fly this over the heads of my friends/family/colleagues all the time. I probably wouldn't fly one around a newborn, but I've had it batted out of the air by a 2 year old in full view of his laughing mother.

I've got some bigger-but-still-small "250" size quads too - all up ready-to-fly weights of around 300g. I'm more careful with those - but I've intentionally flown them into myself with no more protection than a tshirt - and it kinda hurts, but doesn't "injure" me (again, I suspect the mother of the aforementioned 2 year old would think differently if I unexpectedly hit them with one of these in the local park, but it's still in the frisbee or football kind of injury risk - not a "this'll definitely need an ambulance" category. And I at least tell myself I'm _much_ more in control of this than a football or frisbee in flight, and I _really_ don't want to hit anybody).