I've not been following it that closely lately to know if the slowing global economy has had much of an impact on their rapid growth.
I don't like being a "doomsday scenario" type guy with the whole peak oil argument, but it's not like we've got an unlimited supply of the stuff. We're eventually going to run out. And if you want to boil it down to supply and demand, that means it's not likely to gradually become a cheaper commodity, no matter how many dozens of new Priuses you might see on the road any given day.
I'm confident that we'll eventually be able to develop new fuel technologies, and the plan for developing rail transit across the country has gotten me stoked, but I think we've already waiting far too long to get the ball rolling, and we're likely to have a painful (ie: expensive) changeover process ahead of us in the next 10-20 years before we come out on the other side of this thing.