Any folks using private social networking tools in their organization?

Not Elgg–we have tried to use Facebook by setting up a group which is only open to graduates of an international management training program here at CDC’s Coordinating Office for Global Health. Not much luck so far–people still communicate mostly by sending out blanket emails. We are in the midst of developing continuing education for public health management using distance learning, which will include a social networking component. We are piloting it using MS SharePoint–it remains to be seen if this is a good longterm solution.