Most companies view Twitter and Facebook as a great tool to monitor what customers are saying about them. But let's say the worst happens and an irate customer decides to air her grievance using social-media channels instead of reaching out to the company directly. Or perhaps she did try to reach the company via traditional channels (phone, email, etc.) and didn't get the response she was looking for.
When a customer complains on social media, his usual goal is to get the company to respond. The company's goal, on the other hand, is to mitigate or eliminate any negative impressions and show the customer—and the rest of the world—that they are responsive to customer needs. Managed properly, a complaint doesn't have to turn into your worse PR-nightmare come true.