Last night, I attended MICSUG user group meeting. The topic of the meeting was about Microsoft Identity Integration Server (MIIS) to integrate user identities from different data sources. MIIS is a good server for a big company where some legacy systems or departments want to share user identity.
The picture below is an example of MIIS use case. MIIS developer can define attribute mapping for data sources (SQL server, flat file, Active Directory, etc) to import/export identity data.
The current version has limited ability to manage password though. It is understandable that many systems use hash code to store password, so that MIIS can not get original password out. MS is developing password management in next version.
The next version of MIIS can also support Extranet for B2B/B2C identity integration. InfoCard (CardSpaces) will also be supported. It sounds like MIIS will become a good middleware for a big company.