I currently develop a community with an ad-system (DJ-Classifieds). With your new Activity-Stream, the page gets really much more interesting for users. Maybe you can add a plugin for sharing joomla-content directly on the activity-stream? For example: an user has added new ad and now wants to publish the new ad directly on his activity-stream. DJ Classifieds uses "addthis" for sharing. maybe, this can be combined in some way?