First it was the AT&T restricting iPhone users from using VoIP apps on their iPhones to make calls over 3G network but after the investigation by FCC into possible violations of net neutrality, AT&T finally allowed its users to use VoIP apps over their 3G network late last year.
Now, finally, Apple has also removed the restriction. A couple of weeks earlier, Skype blogger reported that they already have a 3G supported Skype version but it’s Apple who restricted them from releasing 3G enabled Skype version.
Now that both the apple and AT&T have allowed VoIP over 3G network, so we can expect 3G enabled Skype version soon.
iPhone Jailbreak community has already been enjoying VoIP apps over 3G, thanks to the VoIPOver3G and Unrestrictor like hacks.