Boo! One of the most popular things to do with a 3G smartphone is to "tether" it, which is to attach it to your laptop and use it as a modem so you can get online anywhere your phone has service. Windows Mobile and Treos have multiple options for doing this -- some even via some sneaky software that works in a kind of "proxy mode" so you can avoid paying the extra costs associated with a full-on "Phone as Modem" plan (which usually runs in the neighborhood of $50 a month). Sadly, AT&T has let the official word out -- you won't be able to do this with the iPhone 3G:

However according to AT&T spokesman, Mark A. Siegel, who spoke with iPhone Atlas earlier this week, AT&T will not be supporting a PAM 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. The latter is charged when a person makes an enterprise type connection to Exchange or a Blackberry server for email or messaging. -- [iPhone Atlas]

Of course, this has already been done for Jailbroken phones and we hope it will be done again -- just don't expect to be able to purchase something like this from the App Store when it rolls out.