On last week’s Windows Weekly, Brandon Watson mentioned that tethering support in Windows Phone would be dependent on the wireless carriers. This is, unfortunately, incorrect. (Which is good for me, in a way, since I wrote in the book that there is no tethering support in Windows Phone.) But it’s been picked up on various blogs.
To be clear: Windows Phone 7 does not support tethering at all.
The intention is to add this capability over time, of course. But it’s not there for v1.