Avaialable on the iPhone
4S, iPad 2 and iPod touch 4G, Facetime is not xpected to work on the 4G LTE network since it doesn't work over the 3G network. Apple has not be able to convince carriers allow Facetime on the 3G, 4G network.
With the current iPhone and iPad 2 it is not possible to have a video chat session via FaceTime to start if at least one of the devices is connected to only a 3G connection. A 4G connection is many times faster than current 3G connections and therefore the measure at least striking. A FaceTime connection would consume about 3MB per minute and can use both 3G and 4G connection, the latter even very simple. In theory gets 4G speeds of 100 Mb per second.
Interestingly, Steve Jobs noted during the announcement of FaceTime on the technique in 2010 would be used over 3G. He said that Apple and some providers had to work to the standard video chat also available via 3G. The question is whether Apple now sits behind the restriction, or that the providers are responsible for fear of overloading.