Even the best investors aren't immune from picking bad stocks.Warren Buffett is one of the wealthiest and most popular investors in the world, so mimicking his moves is a strategy that many of his fans deploy. If his company, Berkshire Hathaway, invests in a stock, then that stock usually sees a boost in its value after investors learn about the new position.But that doesn't mean that every stock in Berkshire's portfolio has been a winner. Three of the company's top holdings have been fairly underwhelming i ...