If you were hoping to make any modifications to your T-Mobile G2, my apologies. Because the phone apparently ships with a rootkit that will override any changes you make to Android and reinstall the original firmware. That ain't right. UPDATED:
According to the New America Foundation, "one of the microchips embedded into the G2 prevents device owners from making permanent changes that allow custom modifications to the the Android operating system." The full 40-page blow-by-blow of the Dev Forum's thwarted attempts can be found here.
Between this and Motorola's Droid X eFuse kill switch, there's an unsettling—and growing—arrogance. An attitude that says you may have just paid for your phone, but you don't own it. Because if you truly owned it, you'd be able to modify it however you pleased. It's like buying a car and being told you can't buy new Bridgestones a month later. Or more relevantly, as NAF points out: it's like installing Linux on a Windows computer one night, and waking up to find Vista back in place.
So that G2 you bought? It's not yours. It's HTC and T-Mobile's. You're just borrowing it, and the terms of the loan are entirely non-negotiable.
UPDATE: Here's T-Mobile's statement confirming the restrictions:
Code-Level Modifications to the G2
As pioneers in Android-powered mobile devices, T-Mobile and HTC strive to support innovation. The T-Mobile G2 is a powerful and highly customizable Android-powered smartphone, which customers can personalize and make their own, from the look of their home screen to adding their favorite applications and more.
The HTC software implementation on the G2 stores some components in read-only memory as a security measure to prevent key operating system software from becoming corrupted and rendering the device inoperable. There is a small subset of highly technical users who may want to modify and re-engineer their devices at the code level, known as "rooting," but a side effect of HTC's security measure is that these modifications are temporary and cannot be saved to permanent memory. As a result the original code is restored.