There have been a lot of questions around Google's approach to federation -- both in the comments on this blog and in other forums (the jdev list, slashdot, etc). I apologize for the delay in responding to these questions head on.
We've updated our FAQ to clarify some changes. To save everyone having to look it up in the Google cache, here is the before:
We look forward to federating with any service provider who shares our belief in enabling user choice and open communications. We do believe, however, that it is important to balance openness with ensuring that we maintain a safe and reliable service that protects user privacy and blocks spam and other abuses. We are using the federation opportunity with EarthLink and Sipphone to develop a set of guidelines by which all members of the federated network can work together to ensure that we protect our users while maximizing the reach of the network. [...]
Here is the new text (changes in red):
We plan to support open server-to-server federation. We do believe, however, that it is important to have the safeguards in place to ensure that we maintain a safe and reliable service that protects user privacy and blocks spam and other abuses. We are using the federation opportunity with EarthLink, Sipphone and other partners to develop a set of best practices by which all members of the federated network can work together to ensure that we protect our users while maximizing the reach of the network. [...]
On top of that, one of my fellow Google Talk developers, Gary Burd, has introduced himself to the Jabber developer mailing list. You can read his first post here.
I, personally, look forward to a long and fruitful partnership between Google and the Jabber community.