A Yahoo! spokesperson confirmed that in-stream ads are being tested within an initial group of advertisers that sell mobile apps and want to present them to Yahoo's audience. Some of them are online gaming companies Kabam, Free, and Machine Zone.
The advertisements seem to be a part of Yahoo!'s broader mobile strategy that would see the former search giant gain leverage on the thriving mobile market. So far, the company hasn't fully utilized the opportunity in has in the mobile space. Last year, the company said that half of its traffic comes from smartphone and tablet users, but mobile revenue "is not material".
In addition to app install-ads, Yahoo! possibly plans to turn part of its homepage into an app platform, tentatively called "Touchdown." It will serve to point the landing page's large amount of traffic at an app-discovery service or some kind of proprietary app-store.