And if you took away the Google hits from people like me that sometimes use it as a quick way to get to some of their favorite sites (I find it easier than going to my browsers bookmarks) Google would have even less hits.
Facebook been took over Google for Impressions. Just not all impression were tracked "Mobile App, API calls, etc". Facebook is the largest Traffic site in the world. 700 million real active user logged in almost all day, checking constantly.
People are constantly logged through mobile apps, desktop app, etc.