Berkshire Hathaway CEO Warren Buffett is out with his annual letter to shareholders detailing the company's performance in 2013 and also offering some sage wisdom on investing. Buffett's letter highlights a strategy used to acquire Heinz as well as opportunities for more investment in energy. Buffett also says Berkshire increased its stake in four blue chip names: American Express, Coca-Cola, IBM and Wells Fargo. Buffett says those investments are a way for Berkshire to increase returns without having to own the companies outright. As for areas of caution, Buffett says over the next decade bad news about public pensions will be front and center. TheStreet's Ruben Ramirez has details from New York.