As the farmers' market season gets under way in the U.S., more shoppers than ever will be supporting local growers and producers. (According to a 2010 Department of Agriculture survey, at least 6,132 markets exist nationally, a 16 percent increase from 2009). While there has never been a more popular time for extolling the nutritional and culinary value of local food in the mainstream media, not everyone is convinced of the economic benefits of local food systems.