I see multiple comments saying that the blades are harmless, but a quick search through google photos seems to imply otherwise to me. Not to mention the force of this thing dropping on your head after it clips a nearby branch, or has a system failure.
I suppose the answer is that the owner needs to be responsible with its usage. The example footage seemed fairly reasonable use-cases (no bystanders).
Yeah, those blades are NOT harmless. They will cut you up on the thinner skin bit and do some serious bruising on the thicker skin. Also, anything around the head is asking for losing any eye or something else.
I've been building and flying quads for years now and Anything over the tiny indoor ones commands a LOT of respect from me due to experience.
The idea of these things autonomously following you is cool but a HUGE liability.
Unless they have some major obstacle avoidance on board they you basically could never safely use this around other people and honestly you shouldn't even use it around yourself.
'harmless' drone blades are the exception, if they even exist. Note that drones designed to operate indoors have some form of protection for the blades (Parrot drone, for instance).
In addition, 'cheap' blades have sharp edges due to the manufacturing process. Some drone owners recommend sanding them to get rid of those, to minimize injuries.
I could think of a pretty much harmless blade design that MIGHT work (soft blades), but they'd be woefully inefficient AND they would only work for those super-ultra-light micro/nano drones.
Anything else is not harmless. Even a tiny quadcopter can easily cut your skin, because the plastic is hard and sharp. Think of it as one of those plastic picnic knives, except not that sharp --- BUT rotating very, very fast.
I suppose the answer is that the owner needs to be responsible with its usage. The example footage seemed fairly reasonable use-cases (no bystanders).