Knowledge Network for SharePoint Server 2007 is the first commercial offering from a new group at Microsoft called the Information Worker Greenhouse (IWG). The software has two parts: a client piece and a server piece.
The client piece is installed locally and indexes e-mail content to create a profile of keywords and contacts specific to that user. By creating this profile, the user becomes a Repository. The user then publishes the profile, and it is uploaded to the server. All the published profiles are then aggregated in the Knowledge Network server and then the SharePoint Server 2007 search service indexes the information created by the aggregated profiles so that it can be returned within search results. The more profiles that are published, the bigger the network and the more Repositories there are to reach out to. When a Seeker searches for information (knowledge), the search results will return Repositories. The results are also ranked by relevance and relative "distance" to the Seeker.
Of course, unless there are some restraints on what Repositories are available to the Seekers, we have potential privacy issues. A user can choose what type of information to include or exclude in his or her profile. There is also an "opt-in/opt-out" feature that administrators can configure. And probably the best piece of privacy protection in the software is that only APPROVED information by the Repository gets sent to the server.