In September 2010, when Microsoft announced they were dumping Windows Live Spaces and migrating users to WordPress, it seemed like news straight out of the Bizzaro World. Their recent blitz of iOS and Android apps for things like SkyDrive, OneNote and Lync has also been interesting to watch, and in a continued shift of direction, Microsoft yesterday announced via the Windows Live blog that they would be extending to the 300 million users of Windows Live Messenger, access via the open standard "Extensible Messaging and Presence Protocol" aka XMPP aka Jabber.
XMPP already powers two of Microsoft biggest competitors in the instant messaging world, Google Talk and Facebook Chat.
Immediately, developers can begin writing clients or plugins for connecting to the Messenger network via XMPP. The current version of your favorite alternative client will not be compatible until they've added support for X-MESSENGER-OAUTH2 Simple Authentication and Security Layer (SASL) authentication and obtained a free client access token from Microsoft. This is to presumably prevent developers from creating or connecting with clients that are intended to exploit the network.
What remains to be seen is if Microsoft will eventually allow Live Messenger users to communicate with other XMPP services, like Google Talk, using their Live ID through what is known as XMPP federation. Google Talk already allows users to communicate with any other XMPP provider that supports federation, so it should just need to be something Microsoft enables on their end.
Once that federation happens, it will really begin to tear down the silos of instant messaging that have existed all through the last two decades since providers like ICQ, AOL, Yahoo and Microsoft began offering the services to their customers.