The Oracle of Omaha is a big believer in concentrating Berkshire Hathaway's capital in his best ideas.There isn't a money manager on Wall Street who commands more attention than Berkshire Hathaway (BRK.A 0.53%) (BRK.B 0.59%) CEO Warren Buffett -- and there's a good reason why.Since ascending to the CEO chair 60 years ago, the aptly dubbed "Oracle of Omaha" has overseen a cumulative return in his company's Class A shares (BRK.A) that's approaching 5,800,000%, as of the closing bell on July 14. This is nearly ...