And, it ignores the variety in the goals of marketers, and the audiences they are trying to reach.<p>For example, on Twitter you can target ads to public conversations among influencers. You cannot do that on Facebook; there are no public conversations among influencers on Facebook. Influencers use Facebook the same way you and I do: to stalk people and avoid their parents.<p>Or consider the quickly growing content marketing options, like branded content (the Buzzfeed and Vice model), buying native content slots on sites, and content &quot;recommendation&quot; systems like Outbrain and Taboola--which are way cheaper than Google or Facebook.<p>Want to reach teenagers? They don&#x27;t use Google and Facebook. You better be on Snapchat and Instagram (and, actually, Twitter). Etc.