Monitor the performance of the campaign

The walled garden restrains advertisers from challenging the performance of the network. It is very difficult to compare the results of a campaign performance between Facebook and other marketing Networks/Tools. It is giving much less transparency about what is really happening and can lead to some errors not being detected in time. 

For example, it is well known that Facebook miscalculated their video average viewing time for 2 years without having been questioned by any other reporting tool.