Former New Jersey governor and Goldman Sachs executive Jon Corzine resigned as chairman and CEO of MF Global, the brokerage firm that filed for bankruptcy on Monday. Corzine has chosen to forfeit his $12 million severance package. Under Corzine's leadership, MF Global lost two-thirds of its market value. A federal investigation is now under way after MF Global disclosed that $630 million of customer money was missing. Corzine is said to have retained a criminal defense attorney. Michael de la Merced, reporter for The New York Times' DealBook, discusses the latest developments.