I like this theory, a lot.A conspiracy theorist would come up with a scenario where Apple was very helpful to Tether in the development of this app knowing full well that the carriers would complain about the loss of the ability to charge for tethering and Apple would thus be required to pull the App.
Apple gets to generate a lot of complaints about an industry practice it doesn't like (data is data)
Tether gets to make a half million before it is pulled.
Carriers once again the bad guys
As an aside, in Oz some carriers initially tried charging for tethering, but others didn't. In the end it is mostly just included in the data allowance. So I doubt too many Aussies bothered with, or had a need for this app. US carriers really suck.
Also, I admittedly thought you were talking about the HBO show for a moment.