The feature will launch to a "limited set of users... from a pilot group of advertisers" in order to gauge feedback from the ads. Promoted apps will be clearly labeled as such, just as they are in regular search results. So far, Google Play's apps search has only used algorithms and human intervention, so the changes could have a substantial impact on results.

Google may have decided to monetize Play with ads since Facebook now vacuums in a large amount of ad revenue for apps from the likes of King -- which spent almost $400 million marketing Candy Crush Saga and other games. Google took in around $10 billion in revenue from Play last year, and paid nearly $7 billion of that to developers.