It seems that a new iOS 5.1.1 error message has shown up that leads the tech world to speculate that Apple is considering implementing FaceTime support over 3G. The warning message is for when you enable or disable Wifi. When you first disable 3G it will tell you it might end your current FaceTime session, but obviously it doesn’t affect it at all. The same happens when you go to re-enable 3G.
FaceTime is a great way to talk to other users using video and the front-facing cameras on your favorite iDevice, but there has always been one limitation- you absolutely must use WiFi to use the service. Steve Jobs had originally stated that the service would be limited to WiFi until it had mobile carriers that were actively interested in the service. Perhaps the time has finally come? It’s hard to say at this point, but if you really want to use FaceTime over 3G now, it is certainly possible, provided you have an unlocked device and make use of a special download that, obviously, isn’t authorized or approved by Apple.[ source ]