According to a recent report from iDevice, Apple plans to allow the FaceTime feature over a 3G connection. iDevice's Zaone explains he was using FaceTime on iOS 5.1.1 and he noticed a revealing clue to Apple's future plans.
He tried to shut down the 3G connection in order to receive a FaceTime call, but an error message appeared instantly. "Disabling 3G will end FaceTime", stated the message. This demonstrates that Apple is testing FaceTime video calls, over a 3G connection.
Despite the warning message, the video call continued on Wi-Fi, even after the 3G connection was turned off. While Apple seems to be testing the support for FaceTime over non Wi-Fi networks, there is no news about how carriers would react to this.
Apple is also believed to be taking a walk on the carriers' turf, with its own VoIP service. FaceTime was introduced back in 2010, with the fourth generation iPhone. The video calling service was then extended to Mac users. iPod Touch and new iPad owners were next in line, to enjoy FaceTime.