Nah, the magic sauce (IMO) was the progressive roll-out. When only .edu addresses were allowed in, it was exclusive and regular joes were desperate to get in. Google successfully pulled the same stunt with gmail, but failed dismally with google plus.
I mean, my entire knowledge of the launch of Facebook comes from watching The Social Network so take it with a grain of salt. But wasn’t he a prolific LiveJournaler (writing about his projects amongst everything else)? I’d think that fits this article rather exactly.