I'd like to point out that one of the authors (Moira Burke) was a PhD student in our department at Carnegie Mellon University (the Human Computer Interaction Institute) and she did research of the highest caliber with a high level of rigor and integrity.
She and her doctoral adviser (Robert Kraut) also published a very good peer-reviewed paper in the Communications of the ACM entitled Internet Use and Psychological Well-Being: Effects of Activity and Audience (https://cacm.acm.org/magazines/2015/12/194633-internet-use-a...) which summarizes about 20 years of research in the area, and the post from Facebook echoes a lot of the same themes. The Facebook post also mentions a lot of other very well-executed and highly regarded scientific research in understanding how social media affects us.
So I'd really like to ask folks to please differentiate between the science side of the post (which I'd say is very good) from any of the associated policy or business issues (which is fair game).