Any way one slices the numbers, the world has rapidly shifted from years of concerns about tight supplies of grains and soybeans toward questions about what to do with all of the surplus production.Yesterday while we were having a "blue sky" discussion about markets in general, a friend (who has no relationship with managed funds that we are aware of) asked us this question: If we were in charge of an actively managed fund that focused on investing in commodities, where would we place the fund's money right now? We threw out sort of a non-answer, but the question got us thinking about commodity markets from a non-commercial investment perspective.The concept of investing is commonly assumed to involve buying some asset and holding on to it...