One of the things missing here is an influence measure. Prediction: ComScore buys Inteliseek by end of year (perhaps Technorati, but that doesn't seem as synergistic). comScore Study Dissects Blogosphere, Finds Ad Audience · MarketingVOX
Update: Rick Bruner had a big hand in this (wait, I thought Rick worked for DoubleClick???) and has a deep background on the study (looks like some form of influence was included).