Yes, the phone will tether on iOS 4.0 or above natively; however, at&t will make you wish you didn't. So this tweak bypasses the signature and allows tethering unbeknownst to another device
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I'm not sure about other carriers from other countries though. You could very well be able to tether free of charge--I don't know.
What is the difference between this tetherme and help.benm.at?
I was using help.benm.at until a few days ago, my iphone 3G tethering option kept disappearing when I tried to tether. It had been doing well since Jan. 2010. Then I installed tetherme and the tethering option does not disappear anymore. Before it disappeared, it worked just the same as tetherme, so what is the difference if my tethering had not stopped working? Why do we need to pay to get tetherme instead of using help.benm.at?