Doc Searls on framing in a blogging article. Market statistics aren’t hard to find, just ask one of the people indexing the darn thing. (Technorati, Feedster, Pubsub, Bloglines…) To read the original article you have to register first—obviously an organization that “gets” the web.
Just use BugMeNot. No compulsory registrations, ever. 😉
http://www.blogwise.com/stats/generators.php
This page is updated every day, based on 40,000 or so blogs, and WordPress has been in the lead for at least the last six months.