Guy Rosen, Co-Founder & CEO of Onavo, the "3 rd party mobile data optimization service" (here) participated in a panel session during the Mobile 2012 conference held in Israel this week.
According to the report in the Calcalist news site (by Reut Miriam Cohen, here, Hebrew), Mr. Rosen was asked about how Onavo is planning to generate revenues from the optimization service.
The answer was - "the possibilities are charging for the application download, advertizing during use, or selling services; for us, the third way is very suitable. We save people money, asking some in return makes sense. In the meantime this is free of charge"