Facebook will launch a second mobile ad product which will serve ads to users based on which other apps they’ve downloaded onto their phones—raising concerns over privacy, according to the Wall Street Journal:
… ads for apps directly in a users’ News Feed on their mobile devices, whether the consumer has noted an interest in that company or not,
Facebook engineers have built technology that lets the company track what apps people have on their phones and target ads based on that information, these people said.
Previously, Facebook largely served ads keyed by users’ own preferences, friends, and their Likes. Sponsored stories, for instance, Facebook’s first mobile ad product, serves ads triggered by users’ brand mentions in their status updates.