I can't remember the name of it, but over a decade ago I saw something like this - it was a single Linux server shared by (I think) hundreds of people. Really trying to do the multi-user paradigm. They advertised it as a private kind of social network, it was invite-only and I think you had to pay to help keep the server lights on.

Hopefully by posting something incorrect, A Person On The Internet Who Knows Better will come along and provide the correct details. :)