Google is the only major advertising company which requires you to use their own ad server (DFP, now known as GAM) in order to compete in real-time with its own

Google is the only major advertising company which requires you to use their own ad server (DFP, now known as GAM) in order to compete in real-time with its own inventory. Since they are the largest advertiser, everyone is basically forced to use Google's ad server to manage all/most of their inventory, including inventory from other advertisers. My understanding from the article is that they were using the data they collected about publishers' other advertisers within the ad serving system to give themselves an upper hand. This is not surprising when you learn all of the other more obvious ways that Google gives themselves an upper hand in GAM.