I'm attending Defrag in Denver this week and enjoying the opportunity to listen and learn. One thing I thought you might be interested to see is a new version of the participation hierarchy that Charlene Li and Josh Bernoff presented in Groundswell. Used to be a ladder, now it's a pyramid.
Groundswell version:

Charlene's new version, as presented at Defrag today:

Li's full presentation is on Slideshare - enjoy.
ADDITION 11/7/08
I remembered that Jeremiah Owyang posted Gartner's version of the above in a blog post back in August:

Jeremiah's post also generated a long and interesting comment thread -- go check it out.