One of these interesting problems: the US has sent hundreds of thousands of tons of food aid to Africa, which are most likely crops purchased by the government as part of the price control process. Yet many countries won't accept it, even though it is the same thing we (or at least most of us) eat every day. The reason? It comes from genetically modified seed. I've seen at least one article that says the reason that they have refused it is because they then won't be able to certify their own food exports to Europe as GM-free.