Food is important, especially when you don't have it. The rule of 3s says "3 minutes without air, 3 days without water, 3 weeks without food" but another saying is, "every nation is about nine meals away from revolution."
It was posited here that the Arab Spring was due in no small part to high food prices for peoples whose food budgets started out at around 40%. For instance, the Egyptian government had a food price support in place, and when global prices rose, it became too expensive for them to run. Down went the Egyptian government, after being in power for 40 years. Check out the "Food" column in the table below and you'll have a sense.
The CPI that a population feels when prices move depends on where it spends. In the US, the food spend is 7% of our income. So if the food price index moves from 125 to 225 (an 80% move) as it did in 2006-2008, we would see a CPI impact of about 6%. For people whose food budgets account for 46% (such as the average Pakistani), they would see a CPI impact of 36%.
What drives food prices? Aside from supply shortages, money printing, increasing population, and oil prices (10 calories of fossil fuel goes into the production of each calorie of food), there's the competition for land from biofuels. But given how mechanised farming is today, Looking at the left chart, it would seem that oil prices are the prime driver, but it could also be money supply too.