Despite hints that Apple's FaceTime may eventually work over mobile networks, it's so far remained limited to Wi-Fi only even on the new iPad. Now we've got another sign that Apple is considering expanding the video calling service to 3G or 4G. An apparently new warning message, first spotted by iDevice, shows up if users try to disable 3G data while on a FaceTime call. "Disabling 3G may end FaceTime," it reads. "Are you sure you want to disable 3G?" Since the call is still running over Wi-Fi, disabling it does nothing, but re-enabling it afterwards gives a similar message. "Enabling 3G will end your phone call. Are you sure you want to enable 3G?"

When FaceTime debuted in 2010, Steve Jobs said that "we need to work a little bit with the cellular providers to get ready for the future" before it would run on mobile networks. Apple has previously declined to comment on FaceTime over LTE, and with carriers looking to video calling as a new revenue stream, Apple may have some touchy negotiations ahead if it truly plans to launch FaceTime over their networks.