AT&T has just announced today that they will begin being less strict on who can and cannot use iOS 6ís FaceTime over cellular feature. Just before today's announcement, AT&T limited FaceTime over cellular to people with the shared data plans.
Now, AT&T states that within eight to ten weeks they will be rolling out the feature for any iOS 6 user with a tiered data plan and LTE capability at no charge:
Originally Posted by AT&T
If youíre not on iOS 6 or you have a non-LTE iOS device, then it looks like youíll still have to rely on a jailbreak to get your FaceTime over cellular fix.
Sources: AT&T via BusinessInsider