Previously, FaceTime over cellular was only available for those using shared data plans. Now it's available to anyone -- as long as you have an LTE device with iOS 6, which means only the iPhone 5 or the third generation of the iPad with a cellular connection.

Watching Impact on the Network

The change for AT&T comes a little less than two months after its biggest competitor Verizon Wireless announced back in mid-September that FaceTime over cellular would be available at the outset, once the iPhone 5 became available.

In announcing the change on AT&T's public policy blog, Jim Ciccone, a senior AT&T executive for legislative affairs, said that the decision to restrict FaceTime had been out of concern that it would cause too much of a strain on the carrier's network because it has more iPhones than any other carrier.

"To do otherwise might have risked an adverse impact on the services our customers expect -- voice quality in particular -- if usage of FaceTime exceeded expectations," said Ciccone. "And this is important for all our customers regardless of which smartphone they may use."

He added, "We will continue to gather and assess the network data on this issue over the next few months and anticipate that we will be able to expand the availability of FaceTime to our customers on other billing plans in the near future."

The change gives users of other phones, including earlier iPhones an incentive to upgrade.

Marginal Difference

Since people generally use FaceTime when they are at home, where wi-fi is available, impact on the LTE network may be minimal.

"It's something not everyone uses all the time so it's not a dominant part of their network," wireless analyst Gerry Purdy of MobileTrax told us. Wireless service providers like AT&T and Verizon figure, "it's not going to cost us a lot, so there is a perceived value. I wouldn't be surprised if this is a cooperative effort between Apple and AT&T."

Purdy speculates that Apple has a vested interest in seeing FaceTime grow as a form of communication that keeps people using iOS devices, rather than looking to rivals like the Samsung Galaxy S III or a slew of new Windows 8 phones.

FaceTime vs. Skype

"When we get to Skype on Windows Phone 8 being out there in the first quarter of next year, you're going to see some interesting things being done," Purdy said. So it's not surprising AT&T is doing this now. "It gives them a competitive edge."

AT&T also announced that FaceTime over Cellular will be available to deaf and hard-of-hearing customers who qualify for special text and data-only packages.