Facebook started out as a stalker/creeper site at Harvard, based on the model of the printed "face books" that colleges distributed with photos & names of students — which other students sometimes used to find sexy classmates.
It then expanded to other US colleges & universities, before opening to the general public.
This gave it an initial user base that was young, rich, & sexually active.
It's that, not the technology, which is difficult to replicate "in the wild".
Diaspora