From http://techcrunch.com/2014/09/05/monetization-automation-enforcement/:

Technically I am also a long-time Facebook user, joining the service back in April 2007. But I don’t think of myself in those terms — and certainly wouldn’t identify as one. I’m still on Facebook, largely for work purposes or to use Facebook as an identity layer for other apps and services, but I am not actively engaged with Facebook. I rarely post anything, log in only sporadically, and — despite Facebook’s position as the undisputed leader of social media services with more than 1 billion active monthly users — feel zero personal attachment to it.

If Facebook disappeared tomorrow I would barely notice its absence (except perhaps in a welcome sense via the sudden lack of spam emails)