I've read about the increase in prices of corn (maize for our European brethren) and think it is due to the interest in ethanol production. The irony is that we can't produce enough corn in order to replace all of our foreign supplied oil (at least without depleting our food stocks).

On the overall question of food stocks, I think that you are refering to local shortages caused by specific factors. In Dallas the stores get cleaned out the moment a single snowflake hits the ground. If we keep several weeks of canned/dried foods in the pantry, we should be able to ride out any specific shortages.

I'm more concerned about the water supply. Even if I have filtration and purification equipment on hand, it won't be useful if water isn't around. The area lakes around Dallas were hit pretty hard by last summer's heat wave. All of the recent rain hasn't helped the lakes rise back to normal levels.