From the Q&A:
Q: Where do you stand on tethering?
A: Theres two pieces needed to support that: client side and working with carriers. Were absolutely supporting tethering in the client side in iPhone 3.0, but were working with carriers around the world to see when they can add tethering support on their networks. But we are building that support into iPhone 3.0.
Are they seriously telling these lies publicly? Carriers (at least in Europe) support tethering for at least 5 years!!! What exactly is Apple working with the carriers on? What a ********.
I think your missing the point, I think they are saying the support is there, its up to carriers to announce plans and basically turn it on.
AT&T announced plans but have yet to offer it officially, so I imagine its just a matter of them turning it on (very un-technical argument).