>Social networks didn't really exist before The Facebook.

Seriously? Of course they did. An easy counter-example is MySpace, which launched several months before Facebook's very first appearance as a Hot Or Not mimic (which predates Zuck by 3 years), and had many millions more users for years (especially while FB was restricted to colleges).

Major competition and a lot of money was going into social media around then (and for a couple years prior), FB is just the eventual winner.