People can use their Windows Live contact information with your site, while keeping complete control of their data. This includes Hotmail, Messenger, and Mobile contacts.
You can build Social Networks using:
This is an HTTP-based service that enables developers to programmatically submit queries to, and retrieve results from, the Windows Live Contacts Address Book database service.
Windows Live Contacts API provides :
The owner of the data controls each view and set of abilities.
The Windows Live Contacts Web service is exposed to clients in a HTTP/GET request interface with XML response.
Try out the Interactive SDKTry out the Contacts Control (Beta)
About the Windows Live Contacts API
Contacts Control Mashups samples: