I've seen a few videos of these things. Just imagine what's going to happen to the rider/pilot if they have to apply hard braking; the wheel will lock in relation to the frame and engine and the whole thing, including the rider will roll forward, out of control! It's a dumb idea I reckon.
Monowheel rider speeds into record books -
http://www.bbc.co.uk/news/uk-england-lincolnshire-37307743
