In the recent years, social media has become a place where emotional roller coaster of the stock markets can be captured. How the Twitter and Facebook users are reacting to different business news can foretell where the index is heading. Knowing this information can help the companies in predicting their market price, top line, etc.
To know more on how social media can help in predicting in stock prices read http://www.investopedia.com/articles/markets/031814/can-tweets-and-facebook-posts-predict-stock-behavior-and-rt-if-you-think-so.asp .