It seems that id Software Quake Live gaming platform has deployed some sort of XMPP service.
The gaming platform has deployed an XMPP server on quakelive.com: See IMTrends report.
It still unclear what the service will be used as I do not have access to the beta yet, but I can bet that it will be a community chat platform, probably with in game chat features.
It seems that gaming industry is more and more relying on XMPP protocol to build its gaming chat community features. This is more good news for the protocol adoption.
Update: Here is a link to a spanish article showing several screenshots: Quake Live chat screenshots.