Sun Microsystem's concept of their future OS GUI
youtube.com
youtube.com
Taking notes about a Web page is a useful idea, that meta-data doesn't have to stick "on the other side" necessarily, but it could. Perhaps that is the one idea from the video where I get the point the presenter is making.
Perhaps for 3D it is true even more so than for 2D that we need to move away from pre-computer metaphors such as "the desktop" in order to find ways to best use them.