1 - A person who has been a member of Facebook since the days when it was a college student-only network site.
2 - A person who joined Facebook when a .edu e-mail address was still required.
3 - A person who joined Facebook in 2004, or the 1st half of 2005.
"I've been on Facebook since Nov. 2004."
"Dang man, you're a Facebook O.G.!"