Dive Brief: 

• Giant ad-buying network GroupM plans to pull all of its clients' budgets from open ad exchanges by the end of the year. 
• Instead, GroupM plans to build up its digital inventory through ad technology and sell through publishers' private exchanges or directly using automated tech. 
• GroupM is arguably the largest media-buying group and wants to avoid wasting money bidding on random inventory and having ads appear on sites that don't offer value. 

Dive Insight: 

Open ad exchanges help level the playing field by allowing smaller fish to bid on the same inventory as firms like GroupM. That's why GroupM is making the switch, but the implications for the industry at large could be interesting. A huge media buyer like GroupM could potentially use its influence to try to get cheaper prices on private exchanges — exchanges the publishers built to avoid having to lower prices.