I just deactivated my Facebook, Quora, and Twitter accounts. Why? I've been off again, on again several times already. I have typically gotten back on because something I was doing seemed to require me to be on one of those services. However, I don't really use any of them much and don't really enjoy participating in their formats. I don't necessarily mind following some of the news I get, but it's mostly just noise. Therefore, I'm trying to reduce the noise I receive. I find I typically get enough news from emails and RSS feeds, anyway. (Okay, so I'm not totally off the grid.)
In every case, I can still re-activate and get back on the different services. We'll see if I do this time around. I can't think of anything coming up that requires I be a member of Facebook or Twitter.