MF Global Blowing Up?

No news out (link will take you to Google Finance for MF). Trading down from $16 to $4 in less than a half hour. Anyone know what's going on??

Here's Google's profile on MF, which provokes lots of theories as to what could be transpiring:

MF Global Ltd. (MF Global) is a broker of exchange-listed futures and options. It provides execution and clearing services for exchange-traded and over-the-counter (OTC), derivative products, as well as for non-derivative foreign exchange products and securities in the cash market. It provides its clients with access to many of the financial markets worldwide. MF Global provides its clients with three primary types of products: exchange-traded derivatives, OTC derivatives and cash products. It provides these services through dedicated broker teams focused on particular trading markets. It provides its clients with trade execution and clearing services for derivative and cash products across a range of trading markets, including interest rates, equities, currencies, energy and metals, as well as agricultural and other commodities, throughout the financial centers.