Bill Ackman has a substantial portion of his hedge fund invested in Amazon and Uber.Warren Buffett took control of Berkshire Hathaway in 1965 and promptly turned the "doomed" textile mill into a holding company focused on insurance. That decision created a steady stream of investable cash in the form of insurance premiums, and Buffett used that capital to build Berkshire into a trillion-dollar company through savvy acquisitions and stock purchases.Billionaire Bill Ackman hopes to emulate that success with H ...