A few weeks ago, I was alarmed to discover Empathy's dependency on the Google version of XMPP, particularly for NAT traversal
It was surprising to see those fears confirmed so quickly with Google moving away from open XMPP connectivity, particularly for multimedia protocols such as voice and video, leaving open source clients like Empathy who put their trust in Google high-and-dry. With Empathy being the default chat client on the Gnome desktop of Debian and Fedora, this is quite a serious situation.
Fortunately, the latest versions of Debian 7 (wheezy) and Fedora 19 (Schrodinger's Cat (beta)) contain their best ever support for VoIP and RTC federation on the server side.
Still under construction, the RTCquickStart.org guide tries to make it easier than ever to put the necessary packages to use - anybody who already runs their own mail, DNS or web server can become their own VoIP/SIP/XMPP provider in less than an hour.
One particular point to note is that TURN servers work equally well for both SIP and XMPP users. Getting close to 100% support for VoIP users behind NAT requires a TURN server. It is possible to mix and match the reSIProcate TURN server, reTurn with any popular SIP and Jabber servers on Debian, Ubuntu or Fedora. Also look at the Turnserver.org project and RFC 5766 TURN server project
I'd strongly encourage those who are concerned about this latest development to come and join the discussion in the Free RTC mailing list sponsored by the Free Software Foundation Europe