Just like anything - the techies and first adopters tend to set the trends. If the HN crowd thinks its useless then it will start to trickle down to Normies, might take awhile though.
About ~8-10% of my Facebook friends quit over a four or five year span. Typically not long after joining Facebook and beginning to contribute (within a year or so). Those accounts have all just been sitting there quasi-dead with blank images, for many years (although they're still on my friends list, and no doubt counted by FB as a user (but not a MAU)). None of them have ever come back alive.