Yep, I read about all those links you posted, and it’s a very interesting application, even though it’s not exactly what I’m looking for.
I’ve also done some more digging on this subject (by searching for “distributed social networking” I managed to find some more), and found Noserub, an app that does about the same as what I had planned (though a bit differently, so I’m going to go ahead with my thing anyway ;-)), and the way it handles friend requests. Unfortunately their documentation is really sparse.
However, NoseRub doesn’t do friend requests as well, but it’s given me some new insights on how to use FOAF ;-)
As for OpenSocial: I looked at that in the past, but it’s not quite what I’m looking for. In fact, it’s absolutely not what I’m looking for. What OpenSocial allows you to do is to load widgets (like Facebook applications) onto a site that supports OpenSocial. Thus, you could insert a contact list application, but that would be hosted elsewhere, and if you want to add people to the list those people will need to use the same application (and OpenSocial) – unless, of course, that application also supports a standard like the one described by Evan. Thus, it would still be centralized – I want it to be application-independent :).