Twittering classes

Twitter, the microblogging service, which limits posts to 140 characters, seems ready to take on the world. It was founded just three years ago and employs only 29 people at its Silicon Valley offices, but the company is riding a wave. Eleven per cent of US based adults with access to the internet use Twitter or a service like it, according to the Pew Internet and American Life Project, a non-profit think tank. Last year Twitter reportedly rejected a $500m bid from Facebook.

As large numbers of users adopt the service, politicians have begun to take part. Where politicians and their followers once chattered, now they tweet. Barack Obama and John McCain both use Twitter, as do a growing number of senators, representatives and, in the UK, members of parliament.

Use this graphic to find the twittering hot spots around the US and UK and to identify the most closely followed tweeting politicians.