'Enable 3G' Setting in iPhone Firmware NOT Fake
Asking whether or not this screenshot is fake is like asking if a perfect digital replica of a photo is fake. The story remains the same regardless of the answer. As mentioned in the original story, the exact wording and text from the screenshot appears in Apple's iPhone 2.0 firmware:
Apple expects the 3G option in the upcoming iPhone to impact battery life enough that it offers the user and option to turn it off.