One major difficulty with leaving Facebook in particular over privacy concerns is that it doesn't really stop the social network from violating your privacy, or letting others do it (often without bad intentions on their part). Aside from its now famous shadow profiles, you've got your friends and family or work/business associates posting things with you in them, photos, videos etc and even naming you (don't think they can tag you though if your profile is shut down). And if you've erased your profile you can't even have the minimal safety of monitoring what gets posted by who, so you can ask them to maybe take it down if it's harmful. We get sucked into FB's network effect in all sorts of ways nowadays if we live any kind of normal social life in a connected society.