1-888-facetime is your friend. They are only open during business hours in the U.S. It's the best feature on the iPhone 4 and I've been showing off my phone using facetime.
It would be way too slow on the 3g network. I like it via WiFi because you can facetime anyone in the world for free. You don't even pay long distance or overseas charges.
dino - try and check the volume button, i had also face this silly problem which untill i checked that my volume was off
silly error but happens at times
yeah i just recently checked out that FTFun site and it turned out to be prettttty good. alot of people on there from all over the world and there seems to always be someone to chat with :] its a good time.