How long do you figure it'll be before someone loses a hand (or a head) to one of these? The rotor tips are the only danger...especially on one big enough to carry a person. For those full-size babies, any piece of gravel or wood on the ground under it could easily turn into a bullet.

Airboats (used in swamps) also have Hugh Jass fans in close proximity to the human driver - that problem has already been solved.

And because they are lighter, these would need less downward thrust than a helicopter, but I agree that debris propelled by downwash could be a hazard. (but even the entire fleet of huge Chinook helicopters' downwash only caused a few minor injuries over past several decades in service.)

It's a simple thing to cover the blade with a net so you can't fall into it, or so it can't fall onto others.
Stuff on the ground being blown around is only a minor issue when it's near the ground at takeoff and landing. This isn't a ground effects plane, it flies. That means any place a helicopter can take off and/or land would be more than safe, as would any field, clean street, parking garage, any place that's clean or free of people and glass should be fine. It's only about 400lbs of thrust spread over (estimating) about 12 sq. ft., so less than 40lbs of thrust per sq. ft. , or less than 1/3 lb. of thrust per sq. inch MAX. I doubt that can create a 'bullet' out of anything. It would take just a tiny bit of common sense to make this issue a non-issue, if there's an issue at all.

Moving this video to CaptainObvious's personal queue. It failed to receive enough votes to get sifted up to the front page within 2 days.