Facebook is experimenting with letting users bill their cell phones to buy Facebook Credits for virtual goods.

The social network is teaming with mobile payment company Zong to provide this service, and the credits can be used to purchase virtual goods within Facebook. These credits are normally purchased with credit cards, and they can also be used within Facebook applications to do things like buy extra weapons in games.

During the initial test, the mobile credits cost twice as much as those purchased with credit cards due to revenue-sharing agreements with wireless carriers. Facebook appears to be making the same revenue off mobile credits as desktop ones, although the company has not confirmed this.

"As part of this test, we are working with Zong to explore ways for users to easily purchase credits and virtual goods by entering their mobile number, rather than credit card information, in the supported application," a Facebook spokesperson said by e-mail. "We will share additional details regarding Facebook Credits for the third party applications and various payment methods as they become available."

The move could be a critical component for Facebook's future revenue plans, as it recently enabled third-party application developers to sell virtual and physical goods in its online store using Facebook Credits as payment. About 70% of the more than 250 million Facebook users are outside the United States, and these users could be in markets where there is not easy access to credit cards but high mobile-phone penetration.

Rumors persist that the social network eventually aims to allow its audience to use the virtual currency to purchase services and physical goods from third-party sites, which would make it a potential competitor with the likes of PayPal and Google Checkout.

Facebook and other social networks can be time wasters, but they also have the potential to be useful tools for enterprise collaboration. InformationWeek wrote a report on this issue, and it can be downloaded here (registration required).