Windows Live ID processes more than 2 billion authentications a day, and is one of the largest communities on the Internet. In order to facilitate the use of Message Assurance, and Security, WISeKey is planning to integrate Windows Live ID Authenticaiton into their commercial consumer portal CertifyID Accounts.
More information on Windows LiveID and how you can also integrate with it is available here : http://blogs.msdn.com/swiss_dpe_team/archive/2008/04/21/windows-live