Not sure why people want it either? 1) it's extremely restricted in use (not even comparable to android tethering), but 2) say good bye to unlimited, AT&T especially can easily tell when your tethering since using a computer to do stuff use much more data online then the iPhone. They can see spikes in data usage and it's an easy excuse for them to pull your unlimited w/o actually proving whether your were tethered or weren't. And if your on one of the normal plans they can force you to pay the extra $ for tethering.
Not worth the risk.