Well at least its your fault if you haven't updated to firmware version 2.0.2 according to AT&T.
There has been a lot of recent speculation and even a lawsuit about the reception issues with the 3g iPhone. First the 3g chip was blamed for the reception issues and then later refuted in a study. Now an internal source at AT&T has shed some light on the issue providing details about what the 2.0.2 update did and how it is intended to fix reception problems.
Basically the 2.0.2 update controls the UTMS power control in the iPhone. To get service, each iPhone requires power from the service providers transmitter and that power is requested by the iPhone itself. Pre firmware version 2.0.2 the iPhone 3g was asking for too much power from the cell towers. When a lot of iPhones asked for too much power all at once the cell towers would run out of power, leaving you with no reception.
I'd like to have some cell phone service so if you have a 3g iPhone (in denver ) do me a favor. Update to 2.0.2 using PwnageTool for mac or QuickPwn for windows or WinPwn 2.5 when it is released (we hear very soon).