My admittedly naive hope was that I could generate interest through online advertising. But traditional text-based and display advertising turns out not to work very well, at least not for encouraging people to download, install, and use an app. Cost-per-acquisition (CPA) or cost-per-install (CPI) advertising, however, is a different story: I made money, on paper at least, in the form of unexpected free advertising, using Flurry's App Circle CPI program.

interesting experience with paying for app advertising and using a cross promotion platform