I think to anyone who has used it, it is plain testament that social networks do not scale. This is a social limitation, not a technical one. What killed the Internet is the centralization of platforms compounded by the commercial interest to "engage" on behalf of both corporations and users. IRC worked because it was decentralized and had no commercial interest, nor did it cater to narcissistic tendencies. No interest to comment for points, and decentralized enforcement where you'd fuck around and simply get banned from the(that) server.

I once read an article about forum quality as a function of the number of users. I can't seem to find it anymore, sadly.

The core idea is there's an optimal number of people. Not enough people and the community dies: not enough activity and ideas to sustain it. Too many and it also dies: it becomes impossible to form social relationships, cooperation dies down, everything becomes meaningless because you don't know anyone, the probability of ever interacting with any given person ever again trends toward zero.

Made a lot of sense to me.