Yes, social media is good for something, but not for telling people about your existance and how fabulous you are or even all your corporate news (which is another way of saying “look how wonderful we are”).
Social media is the ideal place for you to extend your customer service. If someone moans about you on Twitter then get in touch and resolve the issue. If your customer reviews are bad don’t post a rebuttal but instead make contact and see how you can make amends. If people defriend you on Facebook ask them why – and if you don’t notice they are gone then you obviously didn’t value them that much in the first place.
People spend more time talking about negative experiences than they do positive ones. When questioning of a negative reviewer it turned out that his bad experience was actually nearly ten years ago. Track down those with a negative view of you and put some work into making things right.