Ray Wang just wrote an interesting blog about activity streams / filters - http://blog.softwareinsider.org/2010/08/30/mondays-musings-why-next-gen-apps-must-improve-existing-activity-streams/
Reminds me of our actions. By the way, I had lunch with David Pollack during my vacation and we talked about a related idea of his - I've been trying to find time to write about it here but I have been under water doing other stuff. It is on my list .... D.
