Blog stats
I have often heard arguments from people about the number of active blogs and how many blogs are abandoned area spam blogs etc. I think a better way to measure the influence of Blogsphere is to look at the unique visitors accessing the blogs. (From TechCrunch)

More than the compartive numbers the overall influence of the blogs can be judged from stats (Please note that these numbers do not include self-hosted blogs – which means the numbers from some of the largest blogs are not included). Overall you can see that the long-tail blogs remain extremely influential and that there is a vibrant conversation happening.
Some other interesting stats from the article:
In May, 52 million individual people from the U.S. visited a Blogger blog, almost twice as many as the 28 million who visited a blog hosted by WordPress.com (comScore). Six Apart properties, including Typepad.com, attracted 14 million.
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The vast majority of Blogger traffic comes from outside the United States, where its annual growth rate is 38 percent compared to WordPress.com’s 59 percent. On a worldwide basis, Blogger blogs have a readership of 267 million people a month, compared to 143 million a month for WordPress (comScore, April, 2008). The biggest countries are, in order: