Well, so much for my speculation. A reliable little birdie has informed me that it was indeed AT&T that objected to Google Voice apps for the iPhone. It’s that simple.
It most certainly has to be the case that there is a clause in Apple’s contract with AT&T that gives AT&T the right to force Apple to remove apps from the App Store. My only question is: Why does AT&T have the right to force their will on the international carriers? If I recall correctly, AT&T forced NetShare off the App Store and AT&T required that Skype’s voice chat be accessible over WiFi only. What if a foreign carrier wanted to allow its customers to have these features?