FaceTime Does Not Work Over Google Voice

Reason why this is interesting: Google Voice routes your calls through GV's servers to your phone, so it's more-or-less a standard phone call. GV is also a shield so you don't have to give out your real phone number to people. With FaceTime not supporting GV, you're kinda unprotected. Here's the error when you try to FaceTime a Google Voice number from a regular number, also when you try to initiate a FaceTime when you're already in a call with a Google Voice number.

Update: It seems like some commenters are confused about what Google Voice is for. It's not a VoIP service, it's not another communication service. All it does is route calls, in essence, from a Google Voice number to your phone. Just one more layer inbetween a call. Not a VoIP chat, not anything complicated. That is why there's the expectation that this will work.