Will Facebook restrict itself to high revenue vouchers?

As Facebook is now entering the Point of Sale arena in the US with its Daily Deals Offering the question arrises what would be the business model for true payments. Facebook credits are now converted to vouchers and excepted as a partial payment in combination with regular payment methods.

Facebook could be regarded as a closed scheme like American Express or PayPal. Facebook is both the issuer and acquirer for this scheme. If the scheme has a strong brand, functionality and following this tends to be more profitable than the MasterCard, Visa open model with tens of thousands of issuers and acquirers and organized competition. Beeing less of a utility the new Facebook scheme could capitalize on its true value, establishing preferences for certain products or merchants through its powerfull social media platform. So why would Facebook bother to manage the low marging utility payments if it could benefit largely from bringing consumer preference to the retail store and take a large profit from this?  

Would be interested in youre insights so responses are welcomed.