2D is Better Than 3D
http://www.useit.com/alertbox/981115.html

Nielsen, Jakob
Alertbox
1998

Abstract:

Most abstract information spaces work poorly in 3D because they are non-physical. If anything, they have at least a hundred dimensions, so visualizing an information space in 3D means throwing away 97 dimensions instead of 98: hardly a big enough improvement to justify the added interface complexity.