From the inaugural post from the Windows Live ID team's blog entitled The beginning of Windows Live ID we learn
Welcome to the Windows Live ID team blog! This is our
inaugural “Hello World!” post to introduce Windows Live ID.
Windows Live
ID is the upgrade/replacement for the Microsoft Passport service and is the
identity and authentication gateway service for cross-device access to Microsoft
online services, such as Windows Live, MSN, Office Live and Xbox Live. Is this
the authentication service for the world? No It's primarily designed for
use with Microsoft online services and by Microsoft-affiliated close partners
who integrate with Windows Live services to offer combined innovations to our
mutual customers. We will continue to support the Passport user base of 300+
Million accounts and seamlessly upgrade these accounts to Windows Live IDs.
Partners who have already implemented Passport are already compatible with
Windows Live ID.
Windows Live ID is being designed to be an
identity provider among many within the Identity
Metasystem. In the future, we will support Federated identity scenarios via
WS-*
and support InfoCards. For
developers we will be providing rich programmable interfaces via server and
client SDKs to give third party application developers access to authenticated
Microsoft Live services and
APIs.
Over the next few weeks as we complete our deployment, you
will see the Windows Live ID service come alive through our respective
partners sites and services.
I had a meeting with Trevin from the Passport
Windows Live ID team to talk about their plans for providing
server-based and client SDKs to give application developers the ability
to access Windows Live services and APIs. I've been nagging him for a
while with a lengthy list of requirements and it looks like they'll be
delivering APIs that will enable very interesting uses of Windows Live
quite soon.
This is shaping up to be a good year.