There's been a few ruminations on differences between the US and UK versions of t'blogosphere recently. The online journalism review has a long article (referenced by Mr Worstall). Analysing the difference in numbers between Worstall's page and instapundit or the dailykos, he suggests,

A crucial factor in this readership disparity is the vast difference between British and American media.

Surely rather more crucial is the difference in population? There are far more people in the US than in the UK. Hence, greater numbers reading blogs. Okay, as Paul Berger (one of the writers of 'Blog!') points out, the disparity in blog readership is even greater than the disparities in online populations. But there's also the question of awareness. Many US blogs (especially those on the right) are regularly mentioned on talk radio. Here, blogs have yet to get beyond T'Grauniad/Independent nexus. Apart from Belle, of course. Perhaps that's the key to the future--politico-blogs from fictional London call-girls?