Google Talk has been my preferred instant messaging service for years because it federates with other XMPP services. In other words, if someone wants to IM with you, she doesn’t need to sign up with Google; she can sign up with anyone who offers XMPP services or she can install an (open source) XMPP server on her own machine and connect with you with that.
All that is changing. A while back, Google limited XMPP federation, then reinstated it claiming it was done as an anti-spam measure. More recently, the huge Google Hangouts rollout finds XMPP federation at best being shoved to a back seat and at worst being entirely deprecated. Given that http://talk.google.com now redirects to http://www.google.com/hangouts/ it’s pretty clear that Google Talk is a deprecated service–so it’s hopeless to hang onto whatever federation Google Talk itself might provide. Federation lost.
Therefore, I will probably be shifting my default online presence from Google Talk to an account provided by someone offering unfettered XMPP service. Candidates include jabber.org (who I hope have solved their DDoS problems) and DuckDuckGo.