Steve Rubel has pointed to a 4 part "State of the Blogoshpere" report by David Sifry of Technorati.

Slide5

Sifry graphically illustrates the spikes in posts and their relation to news events and highlights how a piece of news generated by bloggers often pre-empts the breaking of the story by the commercial news networks.

"The blogosphere was abuzz around the discovery of a flaw in the basic mechanism of high-end Kryptonite locks, which made them vulnerable to picking with a dime-store plastic pen, and that news flew around the blogosphere for 5 days before mainstream media picked it up, which caused a second spike, as shown by a secondary spike in posting volume, as bloggers discussed the implications."

The implications for PR professionals are clear: they need to track blogging activity in order to be effective:

"A side note: I wonder how much Kryptonite could have done if their executives were keeping track of the blogosphere on a regular basis - it certainly could have helped to avert a major PR problem if they had reacted quickly and offered a recall or a fix before the news had broken in mainstream media."

The full report: