Facebook users now have another way to obtain virtual currency, compliments of application-discovery service and mobile ad network Tapjoy and pay-per-call marketer RingRevenue, but there’s a catch: You must pick up the phone and call advertisers.

Tapjoy and RingRevenue are teaming up on the initiative, in which Facebook users and other mobile consumers who click on in-app advertisements to dial advertisers’ phone lines and perform tasks such as making purchases, obtaining price quotes, or completing surveys will receive virtual currency in return, or free access to gaming areas that normally require payment.

Tapjoy told our sibling blog Inside Mobile Apps that its beta test, featuring companies including Allstate, is already handling some 1,000 calls per day.

The vendor’s Chief Executive Officer Mihir Shah said:

At the end of the day, mobile phones are, after all, phones. Placing a call is a very intuitive action for mobile users, and for many advertisers, it is the preferred action they want their target consumers to take.

This is especially true for advertisers like insurance companies, high-end retailers, and financial firms, which value phone calls because their products or service offerings are complex and often require a more consultative sales process.

With our Mobile Value Exchange, we had all the systems in place to easily credit members for actions that take place from clicks, but no way to manage phone calls.

Readers: Would you click through and place a phone call to an advertiser in exchange for free Facebook Credits or other virtual currency, or other incentives?