I find it interesting that nVidia announces this out of nowhere. They don't have Fermi yet, but they want people to keep waiting for it. What better way to help gamers wait (and not buy Radeon 5xxx) than to announce nFinity with 3D?
Surely, a tactic used to try and damper Radeon sales, when their nFinity performance is probably sorely lacking (required SLI).
Maybe its not "just" a performance issue but a requirement to get multi-display gaming to work, not all GTX285s have three usable outputs.