I think of ITS (the Incompatible Timesharing Network at the MIT-AI Lab) as the first social network.

https://news.ycombinator.com/item?id=31807854

Artisnal means "the algorithm" and "chat" is written in PDP-10 assembly language and MACLISP, and the "editor" and "messenger" is written in TECO.

https://news.ycombinator.com/item?id=35759887

Then there was Jordan Hubbard's infamous "rwall incident" of March 31, 1987.

It was waaaay more than just reported to the local sysadmin, and almost got UCB kicked off the ARPANET.

https://news.ycombinator.com/item?id=35759965

Keith Lynch documented why "History of the Net is Important":

https://keithlynch.net/history.net.html