Janko has a nice writeup on how Google plans to open up Hangouts group video chat functionality to third party application developers, which could be a nice way to further spur adoption as it unleashes innovative developers to create interesting new apps and services with Hangout video capability built in. What remains to be seen is if and when Hangouts will interoperate with other video chatting services.  My feeling is it will not work with any of the other big ones (Skype, Facetime), as those vendors (as well as Google) has a vested interest in driving users to primarily use their own video chat service rather than giving consumers an “out” in subscribing to their platform through interoperation.