http://www.telegraph.co.uk/money/main.jhtml?xml=/money/2008/04/14/ccview114.xml
As the U.S. diverts more and more corn to the (highly inefficient) production of ethanol, less and less is available for exports. Unfortunately politicians and the general public seem to have caught ethanol as the solution to petroleum fuels - which it is not, at least not from corn (Brazil uses sugarcane, which is better). That efficiency is not going to change until someone figures out how to process corn stalks, and not just the ears of corn - which would use the whole plant, rather than only a small fraction of it. Unfortunately, that involves breaking down and changing cellulose, a process that is not going to be easy, or terribly energy efficient at first. Ethanol seems like a great solution to the oil crisis, particularly as gas prices rise, but until we straighten out how to make it efficiently - either taking the sugarcane tactic like Brazil, or figure out cellulose, which opens up both corn stalks or the highly efficient switchgrass, its best relegated to research and the food to feeding people.

The other problem mentioned in the article is that of world consumption and the Malthusian crisis. This has been approaching for a while - you can't sustain an exponentially growing populace, especially not at anything close to the luxury that Americans live in, and which other (developing) countries look at as a model. The question of what a sustainable world population is will be left till another day - it's complicated. However, suffice to say that, although nothing will happen overnight, the more people that are aware and start consuming less the better, and the smoother the impending crises (over oil, food, energy, etc.) will go - which may not be saying much.

Other thoughts?