On a recent afternoon at Walt Disney World, Dennis Robles was cruising around on an electric "mobility scooter" that the park usually rents out to people with disabilities. Mr. Robles doesn't have a problem walking -- he says he was simply saving up energy for late-night dancing.

"I'm pretty healthy," says the 37-year-old truck driver from Brooklyn, N.Y. "Just lazy, I guess."

[...] When scooter demand outstrips supply at Wal-Mart, greeters "evaluate the situation" and make sure that people using the scooters can demonstrate a legitimate need, according to a company spokesman.

[...] Some entrepreneurs are starting to push the vehicles as bicycles without the pedaling.