Previewed at WWDC, launching in the fall.
iPhone 3.1 Beta 2 Disables Unauthorized AT&T Tethering
Tethering is the process by which you can share your iPhone's wireless internet connection with your laptop via USB or Bluetooth. This allows you to have access to the internet from your laptop, using your iPhone as a wireless modem. While tethering officially arrived with the 3.0 firmware, U.S. AT&T customers have been unable to officially take advantage of it.
Shortly after the release of the 3.0 firmware, however, several hacks began circulating allowing U.S. AT&T customers to unofficially enable tethering on their iPhones. The latest beta firmware, however, seems to disable this functionality.
AT&T plans to provide an official tethering solution later this summer, but will certainly require an additional charge beyond the standard data plans.