Is it possible to extend the activity stream in SP2010? Out of the box, the activity only contains data from a user's mysite and profile changes. I would like to feed in a user's activity from other sites within the farm. For example, if there is a team site in the farm which has a discussion board and the user starts a new discussion or posts a reply, I would like his followers to know about the update. The update should only be seen by the user's followers who has access to that team site.
Also, it would be great if you can direct me to an article that talks about the architecture of activity stream.