According to Blogrunner's ranking system the most influential Bloggers are here (from Loic Le Meur). It is generated using the Pagerank system, which is based around the number and “quality” or other websites linking to them. Take a look, most of them seem to be Bloggers from traditional Media (The Washington Post, The New York Times, Guardian Unlimited) and almost all of them are American (congrats on PlasticBag on being the first non-media, British blog I see there).
There is no doubt some insightful commentary on why the traditional media have the most links – is it because most Bloggers (myself included) comment on current affairs rather than come up with original writing? Is this a good or a bad thing? Are original writing blogs “discovered” as easily as they should be? What is my favourite type of cheese?
I don't know, I'll leave it for people brighter than me.