We’re still waiting to hear if AT&T will or won’t charge you extra to run FaceTime over 3G, but Sprint has already come out saying that it’s definitely not going to. Talking to the WSJ, a Sprint spokesperson said “we are committed to our unlimited data, and that means not charging for data consumption based on the application.”
Verizon is as of yet still being cagey on the matter, saying “The timing of any pricing conversations related to future versions of iOS is premature.”
So, the big two aren’t really saying one way or the other, but Sprint is definitely will not. Seems a good way to win over some customer affection (even though I can’t see people using FaceTime over 3G that much).