I got a factory unlocked iPhone 4 from the UK. I live in the U.S. and use a small GSM provider in my area called Cellular One. When trying to activate FaceTime, I was stuck on the "Waiting for activation" screen. I finally called 1-888-FaceTime and was told that FaceTime won't work on any non-supported networks, like T-Mobile, etc. It appears that even though the phones are sold factory unlocked, FaceTime requires a specific server on the network (like visual voicemail) so it won't work on any other network. That is disappointing. I hope that Skype begins to use the video calling feature.