Pingdom takes a look at the Technorati’s top 100 blogs and what CMS they are rolling on. Turns out that 49 of them are on WordPress.
Technorati determines ranking using what they call Technorati Authority:
Authority is calculated based on a site’s linking behavior, categorization and other associated data over a short, finite period of time. A site’s authority may rapidly rise and fall depending on what the blogosphere is discussing at the moment, and how often a site produces content being referenced by other sites.