Not true. If the hydrogen is generated with renewable energies, driving a car such as the B-Class (Mercedes-Benz W245) shown in this video is in fact emission-free. A solar-powered hydrogen station was opened this week in Freiburg, relatively near to Mercedes-Benz's headquarters in Stuttgart:
Fair enough but my point is that these vehicles are not "environmentally invisible". There is still significant environmental impact in the manufacturing, materials, transportation, supporting infrastructure and disposal of the car.
http://www.ise.fraunhofer.de/de/presse-und-medien/presseinfo... (in German -- sorry, no English translation available yet)
Honda R&D Americas has such a gas station in Torrence CA since 2001. I don't know if it's open to the public though. The one in Freiburg is public.