Twitter, one of the 6 most promising start-ups, according to the Guardian

For The Guardian, twitter is of the six most promising firm of the Internet.

"Twitter is about the intimacy of details," said author David Weinberger. "Through it I see small events in the lives of friends about whom I otherwise might only learn the big events when we catch up after long intervals."

Crucially, it has also been picked up by businesses as an easy way to push messages out to their customers.

Co-founder Ev Williams helped popularise blogging with Blogger.com before selling it to Google in 2002.