Yep it's a scam and a very old one here's an example from 1989 - but it goes way back
http://en.wikipedia.org/wiki/Water_fuel_cell
Stanley Meyer was later successfully sued by disgruntled investors, to whom he sold "dealerships". He was convicted of "gross and egregious fraud" by an Ohio court in 1990 after the vehicle failed to work during a required demonstration of the water-fueled car .
Think about it for a moment
If you could split the oxygen and hydrogen apart with less energy than you get from burning it's a perpetual motion machine!
You are creating energy from thin air - strangely some people seem to have no problem with this - but it's much the same as creating matter from thin air and If I told you I had a machine that made donuts out of nothing you'd have me locked up.
Just goes to show a fool and his money are soon on the internet