CNNMoney.com, 3 Nov 2009Warren Buffett's Berkshire Hathaway said Tuesday it will buy railroad operator Burlington Northern Santa Fe for $44 billion.Berkshire (BRKA, Fortune 500), which already has major stake in the company, said it would acquire the remaining 77.4% of the company in a cash-and-stock offer worth $100 per share.Widely regarded as both one of the world's richest men and the