I don't think I can be much help, Brad. I don't know much about the food crisis at all, and I don't really know what Bryan and Rafferty would say. It's not their position that valuations are always 'right', or that derivatives markets are functional in the sense of being some grand strategist for capital.
In general, (speaking for myself) I don't think speculation can keep price booms going for all that long, and often speculation really is stabilising. Like I said I don't know much about the particulars of the food crisis. But I'd be sceptical of a line of argument placing all the blame on speculation - it is one of those convenient arguments that anthropomorphises bad market outcomes into the form of bad people.
Mike Beggs