The big question is what are the starving people in these African countries getting from such deals: if the deals are so good, why did the people in Madagascar throw out the government that signed one of these mega-deals? We should perhaps not be surprised by the findings of a recent (October 2011) IMF study on the matter.
It comes to the startling conclusion that the investment climate of the host country actually weighs very little. What matter much more are poor governance and lack of transparency. This turns the conventional policy prescription on its head! Weak land governance and poor security of tenure for current users seem to enhance the attractiveness of countries for offshore farming.