The constrainst from going from nich market to mass market are detailed in the piece--they are supply side issues and they are technical. The demand-side is taken as a given that there is plent of demand. The reason that there is no substitution effect (ie inverse correlation) between the demand of local food and corn/soy is that the supply is not fully reflecting the demand.

The corn-syrup and ethanol issues are themselves distinct enough to leave out of the discussion. To a first-order approximation, they are not the problem.