It's supposedly Apple that has rejected Skype and Google Voice. If you read Apple's letter to the FCC their agreement with AT&T is to prevent apps that will abuse the 3G bandwidth from making it into the App store, which is why I assume that Skype has been wifi-only up until now.

I'm just hoping that AT&T wasn't right. It would sure suck if 3G performance (for everyone since bandwidth is shared per cell tower) suffered from loads of people making Skype calls and/or Skype performance also suffered from too many other people trying to make Skype calls.