$Millennial Media(MM)$ Mobile in-app ad revenues will surpass PC online display advertising by 2017; Mobile apps, especially games, are monetizing well through free-to-play (a kind of freemium model) and in-app ads. Most of the key markets in the world are expected to move quickly toward in-app advertising models.

The U.S. is expected to be the top source of mobile app-related revenue. App revenues are expected to growth 3.5 times in the U.S. from 2013 to 2017.

India, meanwhile, is expected to see its mobile app-related revenue grow 8.7 times by 2017. That will happen as the result of rapid smartphone adoption. In key countries, smartphone adoption is expected to grow another 2.3 times by 2017.