http://www.youtube.com/watch?v=_FjuPn7MXMs

Take that and extrapolate. Doesn't seem that "crazy" really. Compiz and KWin both already have window animations you're describing. There was even a Wii-head-tracking plugin for compiz that would give your desktop a third perspective dimension. (Moving your head would reveal the edges/bits of the other windows underneath higher ones).

It'd be a neat demo, but it sounds like a nightmare for daily usability, etc.