Sometimes the promise of the paleo-future can give us all wonderfully hilarious visuals such as the excerpt from Wikipedia featured below. It gets us acquainted with the dangers of "gerbiling."
"In most designs, if the driver accelerates or brakes too hard, it is possible that the force applied overcomes the force of gravity keeping the rider at the bottom of the wheel, sending the rider spinning around the inside of the wheel. This is known as gerbiling, because it has some similarity to the situation of a gerbil running too quickly inside of a hamster wheel."
For more great monowheel pictures, (albeit none with gerbiling), check out this site.