Three years after Facebook launched its Ad Exchange that marked an aggressive entry into the use of real-time bidding technology in ad sales, the social media giant is changing direction, causing waves among both advertisers and ad tech firms.

In recent months, as part of its shift in advertising strategy toward mobile, and in particular app-install ads, Facebook has made clear to advertisers and ad tech partners that it is moving away from a reliance on its Ad Exchange, an automated ad selling service.