Elwyn Jenkins, propietor of Microdoc News, attempts to analyze the lifecycle of a story in the blogosphere. There's some interesting thinking here, including the notion that a story is really a network of commentary and the classification of the commenters.
However, no source data or methodology is provided, so it's unclear how scientific the result is. A thin veneer of legitimacy is given by a few real numbers, but I would be leary of accepting the conclusions as fact.