Between May 4 and May 18, mobile advertising network AdMob is giving publishers a 35% bonus on any money transferred over to ads. For example, if you transfer $100 of money made through published ads to actually running an ad yourself, AdMob will add an additional $35 worth of advertising.
With the economy the way it is, I suspect we will continue to see these incentive-based campaigns. It was just yesterday that news came of social search site Scour offering $1,000 in search-based prizes. And Microsoft claims it has had success with its incentive-based programs such as Cashback and Search Perks.