Microsoft has published a case study which talks about two students who have made enough money to take care of their college tuition fees all by developing ad-supported mobile applications for the Windows Phone 7 platform.
Two students Jake Poznanski and his classmate Sam Kaufmann have developed simple game applications on the Windows Phone 7 platform and all their games have become the top downloaded apps in the Windows Phone 7 app store. Sharing their experience about mobile app development, Jake and Sam say that they had a tough time developing on Android and settled for the Windows Phone 7 platform because it was a clean slate for development.
The two students have pocketed over US $12,000 in just 4 months of launching their applications by the virtue of in-app mobile advertisements. You can download and go through the full case study here.