THE beauty of Twitter, the popular microblogging service, is that users have to keep it short: messages can only be 140 characters long. But companies that mine the stream of tweets for marketing and other purposes (see article in this week's issue of The Economist) get much more information. Below is a map of a tweet including all its metadata. The map was published by Raffi Krikorian, a developer at Twitter. It is 18 months old, but it is safe to say that the amount of metadata attached to a tweet has not decreased since.