Yahoo let the cat out of the bag earlier this week, when one of its executives told Reuters that it would begin offering video chat via Yahoo Messenger to both the iPhone and Android smartphones.

The move would bring Yahoo, which already has 81 million Yahoo Messenger users, again to the forefront of chat services and would pose a serious challenge to Apple’s own FaceTime.

Apple FaceTime, a face-to-face video chat, only operates between iPhone 4 users over Wi-Fi connections. Yahoo Messenger, however, would go a significant step beyond FaceTime, offering video chat over 3G and between any capable platform.

According to Reuters, Yahoo VP of Mobile David Katz told them that the app would allow users to call not only each other, but anyone that currently uses Yahoo Messenger for video calls on their PCs. The Reuters article does not mention, however, if video calling between iPhone and Android users would also be possible. If it could happen between phone and PC, then it likely could between smartphone platforms as well.

The Yahoo Messenger iPhone app has not made it into the App Store quite yet, although two other video chat services – Fring and Tango – have already been accepted. However, as Reuters points out, “neither of these apps have the level of mass-market brand recognition of Yahoo, and their impact on a wireless network is probably not in the same league.”

Video chat on Yahoo Messenger could bring this capability to a significantly larger number of users than any of these other services could. Anyone with Yahoo Mail has immediate access to Yahoo Messenger and that’s a lot of people – people I would video chat with, from my mother to my friends. And how much easier is it to get someone to install a Yahoo-something that a “Fring” or “Tango” something?