Fuel cells require hydrogen which can be either in the form of pure hydrogen or "reformers" can be attached to separate hydrogen from carbon. The carbon and hydrogen combinations that are feasible to use in the reformer are natural gas and crude oil derivatives such as gasoline.
The fuel cell is more efficient than the the internal combustion engine The coming widespread use of the hybrid power source in automobiles (such as Toyoto's Prius which now gets more than 50 miles per gallon in town and on the open road) is more efficient than fuel cells and will be cheaper. Therefore, I don't see widespread use of fuel cells in automobiles.
New turbines are very efficient. Modern power plant design uses steam turbines to produce electricity. The leftover heat is recovered and used to generate by thermal turbines in two stages. The resultant efficiency qppraches 80% Therefore, I don't see fuel cells breaking into that market. Neat technology but no viable application except as power in isolated places or as backup benerators.
I rather doubt these hybrids will ever make it into widespread useage without the imposition of draconian measures forcing their adoption. The problems with highly fuel efficient automobiles are cost and utility. You can buy cars today that get high gas mileage. Most sit unpurchased on dealer show rooms. Algore was found of saying in the debates that automakers was eager to make 80 MPG cars. The problem is that consumers aren't eager to buy them. They're small and underpowered.
The problem, as cod aptly points out in post #9, is the storage and transport of hydrogen is problematic at best and frought with danger. Hydrogen is very light (it makes good dirigibles, except for the transport thing) so it is hard to carry enough poundage to get significant range.