A water-run car? It even runs on ocean water, so a drought doesn't affect fuel supply.
It's way too small; hopefully they'll build a larger model soon.
A liter of water will allow the car to run at 80 kph (approximately 50 mph) for "about an hour". There are 3.78 liters in a gallon (I know this because of my milk cartons), which means the car gets about 180 mpg. That's not bad!
Here in California we'd have to use sea water. We just don't have enough fresh water to support our current needs and fuel our cars. The Midwest, on the other hand....
Update, 6/17/08: In line with some of my commenters, "highly unlikely".