Henry Ford, whose Model T ran on ethanol, made the mistake of thinking alcohol for motor fuel could be made in limitless supply. He didn't count on how widespread his invention would become, nor the fact that the world's population would grow so large that there wouldn't be enough agricultural land or fresh water on Earth to feed us all. We may have already passed that point, and the human population is expected to rise an additional 50% or so by 2050. This means that turning vast quantities of food into fuel is a recipe for global starvation. Ethanol will definitely play a role in our future energy mix, but not the starring role its advocates predict.
If we have to choose between eating and driving, little brown people will die of starvation while our newly-skinny chubbos ride around in SUVs oblivious to it all.