Rumours said that facetime would work over a 3G connection but it does not seem to work, it could be that both users MUST be on ios 5? If you want iCrank try and call me as I have the GM installed
I believe that what is/isn't allowed over 3G is provisioned by the carrier. Most carriers would likely be against allowing Facetime over 3G, since they tend to be stingy with bandwidth. I do remember it being announced as "Supports Facetime over 3G dependent on carrier approval" or something similar.