[chinaunix]

XMPP is not usually peer-to-peer. At least where I've seen it used there is a third party middle man (centralization). Fire up an AWS instance, put your own XMPP server on it, and start your own network with your friends. Just keep polishing it and making it more user friendly. Keep it very simple. Give it some functionality, something simple which everyone wants, that Facebook does not have. Facebook won't disappear overnight, but people do want to try alternatives. People are curious. If you make something really easy to use that offers some useful functionality (think of how simple Instagram is), you will get users who will want to at least try it. You can coexist with Facebook. Facebook will not remain popular forever.

Do this project because you want it for yourself. Because you want decentralization. Scratch your itch. Then share your creation with users.