Interesting idea Tim:
You may think I’m getting obsessed with Google News these days. I assure you I’m not but I did think it was quite revealing that when I searched on ‘Edelman Walmart blog’ I got twelve news responses. When I used the site to search for blogs with the same criteria I got 1,458 responses. That means for every news item there were over 120 blog mentions. Going back to my HP item the ratio was more like 1.5 blog mentions to each news item. I guess this shows how the blogging world works.
Neither of us have the time to validate this but I suspect that they vast majority of the blog posts are "echoes".
The echo in traditional media tends to be word of mouth and email chatter. The echo in the blogosphere tends to be text reposts - as in "Nice post on Tim's blog - I agree...".
So, while it would appear that there is more activity, that activity is a manifestation of the medium. The blogosphere in effect becomes a barometer of interest with one of your audiences - bloggers, and their constituents. What it isn't - necessarily - is a reflection of interest by your target audience.
See Katie on this as well...