I just read this one site about fuel cells, and they suggest that a fuel cell vehicle will produce less water than a gasoline vehicle, so the fears of "water pollution" causing problems in cities is unlikely to occur. The site did note, though, that the water vapor was colder than in a combustion engine, so it might not be absorbed in the air as much.
As for the comments about it taking fossil fuels to create the electricity to extract hydrogen from water, that appears to not be an issue. Most of the hydrogen fuel cells being examined right now are using fossil fuels (oil, natural gas, methane) to produce the hydrogen, and as such you do gain energy in the process. (btw, the only thing that such a fuel cell produces is water and CO2. Personally, I don't think the world needs to worry about CO2 production, but that is a topic for another debate (: ).
Oh yeah, here is the URL for the website I was reading:
http://www.fuelcells.org/fcfaqs.htm#from
[ January 29, 2003, 23:50: Message edited by: Fian ]