Facebook may become more than just a social network; it could quickly overtake Skype to become the most popular VoIP application on the planet. Of course, the Facebook is utilizing its year-long partnership with Skype to power the VoIP feature, but many users may or may not be aware of this and it is an independent project.

After testing the feature in Canada, Facebook has introduced a free VoIP calling system through their iPhone Messages app to users in the United States. Users can open a message with a friend, tap on the phone symbol at the top, and make or receive VoIP calls for no charge over 3G or 4G Wi-Fi or mobile network data. This enables free calling to literally all of your friends on Facebook, whether you know their phone number or not.

This feature is currently only available to iPhone users, but it’s only a matter of time (and may not be much time) before it becomes available to users on other operating systems.