The end of cheap grain.
I've said it before: our economy is a food economy. There is no other kind of economy. My baker friends are all complaining a blue streak about the price of flour--some are seing $5.00/bag increases! And don't even get me started on corn ethanol. Even The Economist thinks it's a really stupid idea to turn food into automotive fuel.
An interesting little factlet. We currently spend (a little under) 10% of our income on food. In 1970 it was almost 14%. In 1930? Almost 25%. I suppose that's something to consider...
Chart.