I think there must be several reasons why Diaspora has found an audience. The change to Facebook privacy settings and their mishandling (technical and PR) of this being foremost.
I also think that Diaspora will have to go down a path that incorporates a lot of earlier work.
One place where the jury is still very much out is in the use of a protocol such as XMPP. I can't see the need for it and it will greatly complicate everything. I think HTTP and plain old URLs are good. I think that the foaf+ssl technique for authentication is also good.
Of course there is another issue here. If everything is supposed to be untrackable and invisible, a DarkNet, with a mechanism that will expose or hide items at the will of the item owner, then there would have to be a translation layer between a set of unknown (hidden) URLs and public URLs. This might be better in IP6. It seems excessive but maybe better than struggling with XMPP?