Years ago I made a decision to stay off of Myspace. Fast forward several years and I've applied that same decision to Xanga, LiveJournal, Facebook, Twitter, LinkedIn, Pinterest, and (as much as I can while still owning an android phone) Google +. don't need all the mundane details of peoples lives and they don't need mine; any major announcements (Death, Marriage, Baby) will make their way to me in time.
I have however had several people (none of them interested/capable of hiring anyone) point out that in this day and age it just looks weird if someone doesn't have an online presence, almost like they have something to hide.
I can see the logic in this argument, but it still irks me that this may be required. How would a hiring manager react if he were to ask for a list of my online presences and I really didn't have any? About the only thing I could give him would be my SE credentials.