Hydrogen is not a source of energy; it's a means of conveyance. In order to use hydrogen for vehicles, it must be backed by a powerplant. In addition, extracting hydrogen from water always results in wasted energy. We should be trying to reduce the amount of energy we demand... not increase it.
Fuel cells are not the best solution fir vehicles... plug-in hybrids are. When electricity is least demanded, hybrids could take advantage of the excess electricity not being used at night and reduce the demand for gasoline.