I think you are calling more things social than the word pre-supposes. If you call 4chan "social", then you have the wrong definition - 4chan is a forum, a place people discuss things.
Facebook, or "the social web" as its coined these days, is about the friend graph (ditto with twitter - its about who you follow, and who follows you), not about discussions.
Imho, the web will function perfectly well without facebook - each of the features of facebook such as photosharing, event organizing etc, all have ready replacements. Sure, the friend graph helps you connect easier/faster, but taking it away isn't as detrimental as taking away search.