That one didn't seem like a hoax, just a neat idea that wasn't really possible to make into an actual product. (as in, it kind-of worked but wasn't going to be physically possible to make into a remotely satisfying product)

So a hoax, no?

No, a hoax implies they were deliberately trying to scam people.

It seems like they learned about a neat concept, made a proof of concept that actually worked, but ran into physical reality when they tried to turn it into a reliable product (while being optimistic along the way). It's real hard to stop being optimistic at exactly the right time, and I'd be pretty forgiving if it seemed like everybody was giving an honest effort.

I've read a lot of /r/shittykickstarters and this smells like all the scams there.