MacRumors received this screenshot from an anonymous reader today stating that it looks like Apple is preparing to take FaceTime over the carrier frequencies. It will probably be limited to 3G only, and not Edge. This is all speculation of course.
Unless you are apart of the jailbreak community, you are limited to FaceTime over wifi only, but if you jailbreak your device you are able to FaceTime over 3G via the MiFi app from Cydia.
Apparently it will be up to the carriers to allow or disallow it. What do you think, will AT&T and Verizon say yay or nay?