It seems like common sense that supporting local businesses means keeping more money in your community. I think the rise of Farmers Markets and small business incubators is a sign that people are starting to value local and regional culture/business moreso than large, faceless chains. This is something I still need to improve on, though. Most of my produce and bread comes from local vendors, but a lot of my groceries do not. Some of this is largely unavoidable, such as cleaning products (as far as I know) but I could still be putting a lot more money into the community. But other commodities such as beer and roasted coffee are widely available on a local level. I think encouraging people to go out and support local businesses and raise awareness is something worth doing.
There are limits based on the values we assign to commodities. I bought a farmer's market chicken once. It was frozen and $26. It was not four times as good as Foster Farms. Bill McKibben relates his attempts to get local farmers to produce local bacon and discovering that they break even at $8/lb. Should we be paying $26 for a chicken and $8/lb for bacon? Yeah, we should. But if you give people a choice between paying what something costs to produce locally and sustainably or what giant factory farms cost, they're gonna go with the giant factory farms.
The statistic I probably use the most is that Cuba prdocues something like 3000 Calories per day per person, from one of McKibben's essays (it's in his Reader). I love to compare it to the propaganda pictures showing empty grocery store shelves, and say that the stores are empty because they eat fresher produce. I'm both excited and cautious towards the current warming of relations with the US, because I would hate for Cuba to adopt the commercial food practices of the US. Really, we need to adopt practices they've perfected, like community urban gardens. That is just one great point McKibben makes. He is one of the thinkers we should really be looking towards more, he has an approach to climate change that manages to be urgent, but not overwhelming. It isn't a sort of hippie-radical approach that is quickly dismissed put of hand, but a more academic and reserved approach.
It's too bad a lot of people can't afford to buy local and sustainable food, but that's an entirely different issue. I might have to pick up that book and look into others related to the local economy and food system.