With both Google and Facebook, mandatory licensing of their advertising inventory (within reason) would help competitors grow. Advertisers want to buy on Facebook/Google because they are the only two ad platforms with quality and scale. Companies like Pinterest/Twitter/Snapchat don't have the enough scale to be interesting to most advertisers. Programatic marketplaces (Adwords, etc.) have the scale, but not the quality (too many spammy publishers and lack of identity resolution across the marketplace). If the big two digital ad platforms were required to license their premium inventory, other companies could invest in their products and gain substantial incremental revenues as consumers started using them. With current business practice, you need to reach massive scale before you can even think about monetizing at reasonable rate ($30+ CPM).
