Here's a snippet to whet your appetite.
Much more potent, though, is to use CPA offers to monetize an app’s virtual currency. This is the most inherently social of all of the models. Many apps have a virtual economies where users can earn and spend points (or other virtual currency). Users trade in the “points” to send a virtual piece of sushi to friend or “buy” a pink tutu for their virtual elephant on (fluff)Friends. Sometimes they just want to have the most “points” of all their friends. Developers have long used virtual economies to motivate users to perform viral actions like inviting friends to install the app, but CPA offers give users a chance to earn extra virtual currency. Users might complete a short survey, fill out a lead form, or even sign up for a service like Netflix. In exchange for completing an offer, they earn more of app’s virtual currency. Often times these interactions are real-time, so users can earn the virtual currency immediately, without even having to leave the app.