I read somewhere that at least part of the fall in BDI is due to a massive investment by China in container ships that are empty. So it may be a supply problem as well as a demand problem.
Back in the beginning of the recession, many ships were essentially dry docked because the financing wasn't available to many of the shipping companies. Talk was that if a ship wasn't full and the profitable, it wasn't leaving; so they removed capacity. This time it seems that everyone has run out of answers and is just trying to make money before the shoe finally drops.