There as various reasons for the rapid rise in food costs, and it boils down to supply and demand, as usual. Experts are worried about social upheaval in many developing countries. This picture, from the Wall Street Journal, shows riots in Haiti over food prices, which led to the resignation of Haiti's prime minister. Many people are blaming trade barriers and tariffs, as well as biofuels, as written about in a previous post. Here's this from the WSJ.
"During informal conversations and interviews, ministers mainly agreed that the U.S. policies on biofuels were especially harmful. U.S. ethanol is made from corn, which, ministers said, could be exported to feed the hungry, and benefited from tariffs that block Brazilian ethanol, which is produced much more efficiently from sugar cane." You can read more here.