Seems like breaking down water for hydrogen would make sense if you used non-polluting energy sources that are available now but not mobile enough - solar, tide/wave, geothermal, wind.
Of course, the long-term solution is nuclear fusion - but people are scared of "nuclear" (and rightfully so, as regards nuclear fission) power, because of meltdown threats, radiation hazards, theft of fuel for bombs, etc. - and simply can't grasp that fission and fusion are totally different processes - opposites, in fact. So they oppose any nuclear power. Closed minds. Good thing there aren't any closed minds on this list. (smirk)