Now that we have 3D screens or sources, the only hitch for 3D to become mainstream is 3D viewers, right now you need glasses which are uncomfortable, but maybe soon the Source might change in a way that you don't require glasses at all.
anyways i don't have a solution to that, what i do have is ideas around what FB will look like in 3D.
so when you log into FB, you will basically be entering a space. The space will have things or artifacts littered around. Just like you home and you room, there will be gaming zones, friends zone, communications zones, productivity zones et al.
Friends will be littered around, the distance from you (or your eye sight as seen in many games) will determine their activity, and their closeness to you. This is very similar to the FB algo for status updates, just that the priority of the status update will be measure in terms of distance from you rather then the 2D how high it is on the list terms.
So what happens when you go to a friend, yes, you will actually walk up to him / her. Well tap them and they a blog roll of their current activities will open up, tap twice and their pics will open up and so on. Gestures will be used for other things, like showing their linkages to their friends, maybe some kind of lines extend to other people in that space, again here, people close to them will have a shorter line ( i am actually imagining threads going out of this one person to other people in his / her friends list) and of live chat will be enabled.
Each zone will have a door, you open a door by providing credentials, by signing in some form.
There will also be tunnels to let you import stuff into your FB account, tunnels are nothing but 3D representations of today's interfaces into other apps.
Input methods, well notice i said tap and gestures, yep, has to be touch. how to turn, well think of a small imaginary wheel on the screen, rotating it clock wise will means you rotate clockwise and so on. How to move forward or backwards, well here's the trick, you don't move forward or backwards, the world moves closer or away from you, and that happens by pinching in or out (which is used to zoom today). what about looking down or looking up? well pressure on the wheel (ends of y axis) will enable that. press on -y and release +y and you look up, and so on!!!
and so on and so forth, all tech is already there, only needs to be implemented.
take care