When Arianna Huffington announced plans two-and-a-half years ago to publish a blog, she was greeted with derision by many of the vocation's purists.

The archetypal blogger, after all, was supposed to be a solitary outsider who worked from home - preferably in pyjamas - railing against the arrogance and excesses of the so-called mainstream media. Ms Huffington, on the other hand, was a multi-millionaire author and socialite with a Rolodex of well-connected friends from Hollywood to Washington.