Judging from the carbon emitted from eating food in the US, food represents about 5% of the carbon usage. It's a higher percentage in developing countries, but the power uses of carbon are very valuable and inelastic. By figuring out how to turn food into fuel and doing so for the most expensive fuel at $4.00/gallon, we drive up the price of food to $6 per bushel as a bushel of corn can produce 2.8 gallons of ethanol and $1.42 in ethanol subsidies which has the energy content of 2 gallons of gasoline of which 2/3 of the cost is the petroleum.
So people living on $1/day can only afford 9 pounds of corn if they can find it wholesale in such small lots. 1 pound is 2400 calories. I guess the high corn price is exposing poor financing, competition, distribution and economic incentives in countries with food riots, rather than simply first world corn consumption subsidies.
The Egyptian government wants to build nuclear reactors, but it can't produce and distribute enough subsidized bread to the throngs of plebians. It's like living in a Jerry Pournelle novel.
Sam, at the moment I'm writing this (11pm on Tuesday) there were items on instapundit to the effect that the food shortages reported in the press have been greatly exaggerated.
(Now that I think about it, I'll include the link.