Facebook is preparing the launch of their XMPP connection interface. It means that users will be able to use Facebook with any type of XMPP clients, ranging from desktop to mobile clients.
This is a huge news for XMPP because it consolidates the protocol as the de facto open standard for Instant Messaging and Presence. Facebook adds about 300 million potential users that can now use XMPP for chatting. This adds to large Google Talk figures and the many other large deployments around the world, like Yandex and Live Journal. XMPP could become the most largely used instant messaging protocol in the coming months!
Facebook announced on their developer blog they had the intention to support the XMPP protocol in May 2008: Using Facebook Chat via Jabber.
We are proud that this XMPP support is built on a customized ejabberd XMPP server as announced several times by Facebook development team, including one of their latest conferences in Edinburgh in September 2009: Functional Programming at Facebook by Chris Piro and Eugene Letuchy.
The missing piece is currently what login and password to use to connect, but I am sure it will be announced by Facebook in due time.
Good job Facebook team!
Update 10 Feb 2010: Official Facebook XMPP support has been launched. Read Facebook Chat Now Available Everywhere.