Offerpal Media, a company which offers virtual currency payment alternatives for social games, announced on Tuesday it's acquired Tapjoy, a provider of monetization and distribution services for the iPhone and Android.  The financial terms of the deal were not disclosed.  Offerpal has raised around $15 million in total funding from investors including D.E. Shaw Ventures, InterWest Partners and North Bridge Venture Partners.

The move shows Offerpal is clearly looking to take a big step into the mobile application industry.  Right now, Offerpal's services enable social gaming users to earn virtual currency by letting them view ads or sign up for free trials, much like gWallet currently does.  It's basically an alternative to spending real cash on virtual currency.  

Tapjoy's platform lets mobile developers embed virtual goods storefronts with the ability to process microtransactions onto their mobile apps.  It also has a built in ad optimization layer and application analytics.  Offerpal said it plans to expand its virtual currency monetization model by leveraging Tapjoy's leadership position in the mobile realm.  

The Tapjoy story began with its founders building iPhone gaming applications like TapDefense and TapSudoku.  Since then, its evolved its business to what it is now and seeing some success.  The company said, it has about 1,000 mobile developers using its services.  It also said it's, "highly profitable" and its annual installs, user base and revenue is expected to quadruple this year.  Tapjoy boasts its reach extends to over 35 million consumers.  It achieved all this with only one mere round of funding, $600,000 from Tugboat Ventures back in 2009.

“Our goal is to help mobile developers improve their applications, grow their user bases and generate higher revenues, and through this deal with an industry leader like Offerpal, we can now do all of that more effectively,” said Lee Linden, Co-founder of Tapjoy.