I may be assuming ill intent where there is none, but I feel like that's part of the plan of the entities (Google, FaceBook) that automate recommendations: get you to discard that nagging feeling like you're missing something of actual importance, and just get your info from the feed. If I were nefarious and had their real estate, I would certainly like to not be transparent so that I could manipulate things without people being able to tell or complain.