Transportation is 40% of U.S. emissions, as I understand it. And the way to make people be more efficient (in all their choices, including how or if they go to burning man or any other driving vacation) is with the market, which is why this idea is interesting. I think it does attack the biggest issue we can easily address. Everybody would like to stop the coal fires too, but that requires different tactics. In the developing countries, we can control what we do with the things we burn. We should also stop burning coal in power plants. The short term answer there seems to be nukes, though eventually other technologies should be able to come in to help.