PLATO Notes
A bug-reporting tool on PLATO that turned into one of the world's first discussion forums.
David R. Woolley, aged 17 and working at the University of Illinois, wrote Notes in 1973. The brief was mundane: users needed a way to report problems, and system staff needed to reply underneath the same post. The structure — a base note with responses threaded below it — turned out to suit everything else too, and in 1976 Group Notes let anyone open a discussion file of their own.
Its influence reached well beyond Illinois. Notesfiles copied the model to Unix in 1980, and Ray Ozzie, who had worked on PLATO, took the idea with him when he built Lotus Notes. A bug form thus became the ancestor of both web forums and enterprise groupware, which is roughly how these things tend to go.