I believe hydrogen cars right now is more hype than actual reality. The two primary reasons for forming that conclusion are infrastructure and safety. Right now, the major inhibitor for any competitor to the gas-powered cars is the vast network infrastructure of readily available gas stations. We tend to take it for granted, but there is a lot of logistics involved in refining the oil and transporting it to the various stations in a timely manner. One only need look to the oil crisis of the 1970's to see what a crippling effect the shortage of oil can present. Now imagine trying to create a brand new hydrogen infrastructure from scratch. This is not a trivial task, for it requires vast capital expenditures. Back in the old days before the formation of the EPA, it was very easy and cheap for the oil companies to sponsor the creation of a chain of gas stations. Now you have to perform environmental impact studies and apply for all sorts of permits. Even if you had a philanthropist willing to put up the money to fund such a venture, just wading through the governmental red tape will take years to resolve. So the cost and time to commit to build such an infrastructure is a very risky proposition for any public or private entity to assume.

The second biggest factor that needs to be resolved is the safety issue. Remember the Hidenburg airship explosion? That was filled with hydrogen gas. Also, believe it or not, the hydrogen bomb is more powerful than an atomic bomb! Hydrogen is a very volatile element to keep stable in any one place. Any small spark could easily ignite it, especially in a car crash. Along the same lines, in this age of terrorism, we don't want to make it easy for people to convert hydrogen cars into an explosive bomb. Right now, there are car bombings attacks in Baghdad. Now imagine that some terrorist here in the US decided to crash his hydrogen car deliberately into a federal building. Unless the safety issue of hydrogen is somehow addressed, there is very little possibility that the hydrogen car could be a viable replacement for the gas-powered automobiles. Our best bet right now would be to bank on electric or hybrid cars, since they can utilize the existing gas station infrastructure, or be charged from your own homes.

Hydrogen cars will be niche products at the luxury end of the market. Why?

Hydorgen is only a storage medium for electricity, a hydrogen car is basically an electric car with a fuel cell and tank instead of a batter, and if compared to storage in a battery is much less efficient. Take 100Kw of electricity and you only get about 25Kw back in your hydrogen car but 70Kw back in your battery electric car. Then there is the infrastructure problem. More details here: http://pbjots.blogspot.com/2008/07/hydrogen-vs-electric-cars.html

However, hydrogen does have one big advantage and that is range. This would explain why most car manufacturers have dropped their hydrogen car programs leaving a few aiming at the luxury market.

Not sure why I can't comment on answers, but in response to Phoebe, isn't another significant advantage of hydrogen that you can refuel in a matter of minutes, rather than waiting 12 hours or more for the batteries to charge (as might be the case with electric cars)?

Don't get me wrong; I don't think hydrogen power is any better efficiency-wise, but it has major advantages that a consumer would value over battery-powered cars.

I think it is very possible for hydrogen cars to happen because it is very popular and maybe even the norm in ten years or so. The only reason we don't have hydrogen cars right now is because people in the government have a lot of ties with the oil corporations. I think with Obama as president now there might be a better chance of hydrogen cars. They have all the technology for a hydrogen car right now they can be making them and selling them as we speak but they aren't so hopefully something will change this and they will start making hydrogen cars.