I think your assertions may be correct and you'd still be off in that the some large fraction of the money facebook takes from big companies came from advertisi

I think your assertions may be correct and you'd still be off in that the some large fraction of the money facebook takes from big companies came from advertising avenues subject to exactly the same risk of being ignored. Think billboards, train stations, toilets, tv, cinemas. All of those could be ignored and are often unrelated to the activity conducted at the time. The value of Facebook if nothing else is that it is one central point to reach everyone's eye at any point in the day. So for the non-data driven decision maker, Facebook at worst will be no worse than other low-yielding "mindshare/brand awareness" channels and is at least current and conveniently executed. (consider the admin that goes with negotiating and conducting lots of adhoc coverage with each channel)