A thought about where "social networking" could go : instead of just being "a thing that lets you post messages for your friends", the permission groups on social networking could be "the equivalent of AFS-style permissions and groups on the internet-wide massively parallel computer"
If this is combined with a shift of UI metaphors from "desktop, file, etc" to activity and shared artifact it could provide the mechanism of access control for all of the things we do on computers once we start wanting to share not only the finished products, but also edits, revisions, etc, with friends.
