The SF Chronicle published an article on May 13 analyzing Yahoo Japan's success, which serves as a sharp contract to Yahoo's success or lack thereof in the United States.
The full article can be found here: http://www.sfchronicle.com/business/article/Unlike-its-U-S-counterpart-Yahoo-Japan-s-7465980.php?t=214c1b6d5d9c45373f&cmpid=twitter-premium