When deciding whether to buy, sell, or hold a stock, investors often rely on analyst recommendations. Media reports about rating changes by these brokerage-firm-employed (or sell-side) analysts often influence a stock's price, but are they really important?Let's take a look at what these Wall Street heavyweights have to say about Marathon Petroleum (MPC) before we discuss the reliability of brokerage recommendations and how to use them to your advantage.Marathon Petroleum currently has an average brokerage ...