Just what is the point of Twitter? It’s a question that users of the ‘micro-blogging’ service will have been asked many times by those who are not converts. Unfortunately, Twitter's new chief executive, Dick Costolo, doesn’t seem to know the answer either. "I am working on clarity around that at the moment,” Costolo admits. “I am currently trying to define what Twitter’s purpose is in the long term. We will be able to be more specific on that answer in the near future.” Jack Dorsey, Twitter’s co-founder and chairman, says: “It is hard to speak about Twitter’s vision without factoring in how much of its purpose has been defined by its users over the years.