I've quit Facebook and I can only confirm: nothing magical happens. At least I feel a bit better and feel less social pressure to accord to certain standards/do certain things.
For a long time I thought LinkedIn is super essential and it would be complete non-sense to quit it. But I'm barely in contact with people I connected with there. Especially I rarely connect with recruiters because this would just be too much noise - of course I write them though. But now I start wondering, there are dedicated career websites and it's anyhow much better to apply for jobs one actually likes - instead of just saying yes or no to what recruiters think is the best idea.