iPhoneAtlas received confirmation from AT&T that there will be no laptop tethering option for the iPhone 3G. With many existing Smartphones, customers can connect their phone to their laptop for use as a 3G modem. This is commonly described as "tethering" and allows individuals to use their phone's 3G connection from their laptop.
AT&T will not be supporting a [Phone-as-Modem] plan for the iPhone 3G. The only available data plan for the iPhone will be the new $30 consumer unlimited data and visual voice mail plan and the $45 business data plan.
Apple will be launching the iPhone 3G on July 11th.