MF Global, the securities firm run by former New Jersey Governor Jon Corzine, was forced to file for bankruptcy protection Monday. The company, at Corzine's urging, made big investments in European sovereign debt. Those bets turned out to be losers. Analysts don't believe MF Global is a harbinger of bad things to come. It was much more exposed to European debt than most U.S. financial companies. Zoe Chace reports for NPR's Planet Money.