Good news for those who thought that FaceTime feature may spend your carrier minutes. Yesterday Apple representative told BusinessInsider that it is not true:

"The voice call ends as soon as the FaceTime call connects. The FaceTime call is over Wi-Fi so does not use carrier minutes."

That really wasn't so obvious because there was a possibility that voice call would keep running in the background in cases if Wi-Fi signal went out or video chat dropped.

The reason why FaceTime feature doesn't work in 3G networks is that it is not decided how exactly such videocalls must be billed - as data toward monthly data caps or in some other way.