Ford sells a lot of natural gas vehicles, the new Transit Connect, for example, is offered with a natural gas conversion from the factory.

The issue with natural gas though, is that you can't just run a pipe from your home line to your vehicle. The natural gas needs to be compressed to a high pressure to work with a typical tank and vehicle.

The pumps required to do this are quite expensive (and quite large). They also require a lot of maintenance to keep them safe. Therefore, the only people that tend to use natural gas conversions are fleets; especially fleets where their driving is contained to a relatively small area. Colleges, for example, are big on natural gas vehicles.

It's good technology that we're able to effectively employ right now. However, like gasoline, natural gas is a finite resource that requires a lot of work to obtain. Switching from gasoline to natural gas wouldn't really help us all that much in the long run.