I work in the natural gas pipeline industry. Until recently when an abundance of natural gas has been found, we studied ways to make hydrogen gas from seawater using nuclear power, or solar power in a desert area near an body of seawater. The gas could be either blended with low grade natural gas or replace natural gas since the gas infrastructure is already in place in the lower 48. I can see them using hydrogen in Hawaii since ALL of their fuel has to be imported. Using solar or geothermal in Hawaii to produce hydrogen would work there. In Nebraska, it probably would not be cost effective or in Texas where oil and natural gas is abundant. Right now there is no infrastructure in place for hydrogen, there is for natural gas, and recently GM and Chrysler are going to start making natural gas trucks off the assembly line. Gas companies around the country will buy them for service trucks.
The Navy has considered using excess nuclear power on aircraft carriers (redundancy is built in, double what the need max) to make synthetic jet fuel from sea water and air. They would take carbon out of carbon dioxide desolved sea water, along with hydrogen, and build the hydrocarbon chains to produce the jet fuel. This would eliminate tanker ships keeping the jet fuel supplied to carriers. It is technically too expensive at this time to do this commercially on a massive scale without an abundance of electricity. I could see in working in isolated areas like Hawaii where they have an abundance of sea water, geothermal, and solar energy to produce it. However, in the 48, the infrastructure is not there, but oil and gas are. Also the further away you get from a large source of water to extract the hydrogen, the more costly it is. We would first have to have about 50 new nuke plants just to produce the electricity for massive production needed to replace our oil based system. Synthetic oil from algae would be less costly.