http://www.theatlantic.com/doc/20100...-local-produce
Food deserts. In poorer parts of big cities, there are often no grocery stores at all. Just convenience stores and gas stations. Which is a big deal if you are someone without a car, or have a limited income.
I've spent a lot of time in an urban walmart. The kind of walmart where almost no white person shops. I can attest to the fact that the average poor person buys lot of processed food junk. And meat.
Let me also add that Walmart is the cheapest source for ammunition in the country.