Citigroup's largest shareholder has been quiet during the bank's recent struggles. In fact, we've barely heard a peep from him since Chuck Prince was deposed as CEO. But wouldn't you know who knocked on the door this morning and raised his stake in the bank to 5 percent, at the bargain-basement price of $5.42 a share? Alwaleed strongly believes Citi is undervalued, he said. We'll see. [Bloomberg]