I have done this before. I have a love/hate relationship with Facebook. When you deactivate your account it still stays there, somewhere, just as you left it, so if you decide you have made a mistake you just sign back in and there it is. Now when I say I have done it before I don't willy nilly chop and change, my absences can stretch years before I decide I want to go back.
This may seem pointless to some of you guys but for me its in the decision to make the break. I remove the book marks from my browser and have in effect removed the temptation, there is something empowering in the knowing I deactivated it that stops me from signing back in. Still having it there and telling myself to not use it would not work for me personally.
If you were to decide to cull one thing from your online time, the thing that added least value to your days what would it be?