Facetime is too integrated into an iPhone that it's easy to miss that it even exists. I've talked to people who use video chat apps on their iPhone 4, and didn't even realize that facetime exists, or how to use it. You also can't get a list of facetime contacts from the phone, you have to memorize if your contact has an iPhone on that phone number or email address or press the small facetime button on the person's contact detail screen on the bottom right corner and see if it will work. On top of that you can't use it on 3G network, which kills most of the use cases for it.