FaceTime allows users to video chat with friends. However, it requires Wi-Fi which means you can’t use anytime you want. Source said they have discovered the above screenshot in the latest iOS 5.1.1 suddenly. It could means people could be able to use FaceTime over 3G again.
If you have jailbroken your iPhone, there are actually many jailbreak tweaks that can do the work. For instance, 3G unrestrictor allows you to do such thing. But, bringing it to become more official is good for all users.
Although it would allow users to use the faceTime more convenient, it could probably eats lots of data. Sadly, only Sprint is offering unlimited data plan.