This NullRiver fiasco is another lame decision by AT&T that shows how much Apple understands the market, and they don't.
Tethering, as I've previously pointed out, already works on Nokia and Windows Mobile phones very easily and has driven the sales of data plans before.
Now along comes a device that requires a data plan and Ma Bell plays the Grinch that stole Christmas, making it a contractual term between they and Apple to not enable or permit any software that would make the iPhone a Wireless Modem.
Since AT&T already has price plans for this kind of thing, called Laptop Connect, all they need to do is charge $15.00 more and let the people who want it, pay for it. I know I would.