From his office in Omaha, Nebraska, without even the benefit of a computer, Warren Buffett has racked up an investment record that far surpasses his counterparts on Wall Street--or anyone else in the world, for that matter. While traditionally stock exchanges have returned about 11 percent annually in the past half century, Buffett's investments have by nearly 29 percent a year, solidifying Buffett's conglomerate holding company, Berkshire Hathaway,...