Apple says that in iOS 6 FaceTime not only works over WiFi, but also over cellular networks, “so you can make and receive FaceTime calls wherever you happen to be.”
That’s all fine and dandy, except not all carriers might be ready to allow such traffic on their airwaves, according to an analysis by MarketWatch
The market research firm notes
that none of the iPhone carriers in the US were willing to comment on the matter, except one spokesman from AT&T who said the operator was "working closely with Apple on features disclosed for iOS 6, and we'll share more information with our customers as we get closer to launch."
That pretty much sounds like there will at least be extra charging for this feature, if it even gets supported at all.
MarketWatch specifically outlines that FaceTime's appetite for data consumption is part of the reason why the service wasn't initially supported over cellular.
Adding insult to injury, these cellular networks “were once dominated by subscribers with unlimited data,” MarketWatch says, citing industry sources.