I joined pretty early when it was still invite only and mostly university population. Perhaps it was described that way because of being invite only but the membership has always been normal, non-elite people (like me).
> The founders had initially limited the website's membership to Harvard students; however, later they expanded it to higher education institutions in the Boston area, the Ivy League schools, and Stanford University.
From wikipedia:
> The founders had initially limited the website's membership to Harvard students; however, later they expanded it to higher education institutions in the Boston area, the Ivy League schools, and Stanford University.
~ https://en.wikipedia.org/wiki/Facebook