Brands use Twitter for four main purposes: listening to customer feedback, helping customers with issues, talking with customers, and selling products and services. Pepsi's marketing director notes that Twitter allows brands to gauge customer sentiment. The document discusses how several brands, such as Eurostar, O2, and the Red Cross, have effectively used Twitter for listening, helping, talking to customers, and generating sales leads. It warns brands to avoid sneaky sales tactics and to be careful what they tweet, as customers will find out.