EDIT
So far, Americans are mostly bystanders in the game, content to grumble at the gas pump and complain in the grocery aisles. As a “First World” nation, the United States so far has not been subject to the food riots, which we have seen in Haiti and other parts of the world. Americans have more per capita income than much of the world; hence the crisis of the Third World, so far, is inconvenience in the “First World” and in developed nations such as the United States.
That said, however, we must understand that this situation is not sustainable. While Americans do have more disposable income than the rest of the word, that income is not unlimited and our food supply is much more vulnerable than we think. When it comes to food security, both in terms of supply and accessibility, this country is much more vulnerable than we think. As one retired grain salesman noted, most of the nation’s grain is moved around the country by just TWO railroads. Little is stored in the event of disaster and the whole system is extremely vulnerable. While we in the United States look at the food riots in other countries with a sense of disbelief, we are not immune. Under the right circumstances, we could be in the same boat. (Ibid)
In order for riots to break out the whole food supply doesn't have to be wiped out. It just has to be threatened sufficiently. When people realize their vulnerability and the fact that there is no short-term solution to a severe enough drought in the Midwest they will have no clue as to what they should do. Other nations can't make up the difference because no other nation has a surplus of grain in good times let alone in times when they are having droughts and floods also. (Robert Felix, “US Food Riots Much Closer than You Think”)
Critics say the US is currently too preoccupied with foreign excursions and oil to pay attention to food security, particularly how concentration of suppliers and processors threaten the food chain. The highly concentrated meat processing industry has generated millions of pounds of recalls this year. Outbreaks in e.coli and other food borne pathogens continue to haunt the headlines, as food prices rise around the world.
The concentration of food processing, cultivation and distribution into the hands of a few companies is wrecking havoc around the world. A Canadian reporter noted the connection between market concentration and price increases around the world: in Mexico and most other countries, a handful of international companies is controlling more and more of the food production line—from growing crops to purchasing crops from farmers, to warehousing, processing and distribution.
EDIT
http://www.indybay.org/newsitems/2008/04/12/18492403.php