Update: Google has now posted that the issue has been resolved. "All services are gradually returning to normal. We will update when full service is restored."
Some of Google's Gchat and Hangout users are having their communications rerouted to unintended recipients. The glitch is causing unrest among those who rely on the two Google services (reasonably so), and could potentially be a serious breach of data.
The issue is reportedly affecting people who are using gchat who haven't yet upgraded to Hangouts. Google has merely upgraded its Talk Apps Status page, saying it is investigating the issue. Peter Szilagyi from Budapest should perhaps have the last—and best—word on this, however.