Erryl, you've made some of my own points why a high cost of energy leads to a rise in food prices.  The USDA had another.  That the countries with large foreign exchange reserves (many are oil exporters) are buying up food in excess of their needs.  Simply because they are concerned about food security and have the money to throw out even at record prices.  

erryl:

greater farm efficiency will lower the cost of food over time... most of the world has plenty of room to increase efficiency (though I hope that they all don't choose to do it with genetically modified food, like the US)

The USDA report argues that there has NOT been much R&D in improving crop efficiency.  They say that world governments have become complacent due to  the stable food supply in past decades, so they haven't put up much R&D money.  And the private sector has concentrated more on reducing costs than improving yields.  I was surprised to read this, but the USDA is the expert, so I'll defer to them.  That's not to say crop efficiencies won't improve in the FUTURE.  They undoubtedly will now that the world knows their food security is at risk.