I'm going to go out on a limb here and guess that the vast, vast majority of Facebook users (like, 90%+ is my SWAG) don't do any tuning at all. I'm also going to guess that a large percentage of users "friend" people they aren't friends with in real-life, due to just "shared common interest" or whatever. IF both of these assumptions hold, then the scenario the author of TFA is painting, could well be true for a significant portion of Facebook users.
Whether that's actually the case or not would be hard to measure. But to share one more anecdote: find my Facebook feed to be less and less interesting over time. With little "tuning" on my part, FB is doing a pretty crap job of figuring out what I actually want to see.
So... I could do the work to go in, delete less-than-useful "friends", tune my preferences, etc... or I could just slowly begin to drift away from Facebook, logging in less and less frequently and using Twitter and/or G+ more. Guess which one is more likely?