After reading the Reason report, I wonder about the weight of these vehicles. It said a 6500 lb. Hummer would be about 1000 lbs heavier if equipped for hydrogen (roughly 15%). That's got to have a negative impact (i.e. cost more) in maintenance of highways, etc.
This thing has not been thought out. It is just another push to get taxpayer money to support their folly, with the help of junk-science.
It is interesting reading the comments of the believers in the free lunch. It takes 1.5 times more energy to split the water molecule than the resulting energy produced. All things being equal, I imagine the Arnold backers will look to the gubmint to make up the difference.