After Google with GTalk (~ 180 million users) , now also Facebook 
(> 400 million users ) has switched its chat protocol to Jabber/XMPP ( pdf introduction). Now you need simply a generic xmpp client (like Adium, iChat, Miranda, Pidgin) and configure Facebook, Gtalk,..XMPP is now the de facto the Standard protocol for Instant Messaging
We should not use anymore chat systems/operators that use proprietary standards like Skype, MS Messanger and Communicator, ..
We are next to have an Interactive Internet: like emails that can be sent out of a domain, we'll be able to chat with people outside our domain: with my gmail account I'll be able to chat with facebook people !!!!!!!!!!!!
The new facebook chat (chat.facebook.com) runs an OpenSource software witten in Erlang, ejabberd (commercial support at process-one.net). That will be also used by the next moodle 2.0.
See the video "Set-up an Enterprise Instant Messaging server in 180 seconds"
