An unusually dramatic congressional hearing on Yahoo Inc.'s role in the imprisonment of at least two dissidents in China exposed the company to withering criticism and underscored the risks for Western companies seeking to expand there...[Yahoo! CEO] Mr. Yang apologized to the mother of journalist Shi Tao, who was jailed after Yahoo China, then a unit of the company, handed information about him to Chinese authorities in 2004...Mr. Yang said: "I want to say we are committed to doing what we can to secure their freedom. And I want to personally apologize for what they are going through."