Facebook hider 

Someone on Facebook who consistently has a profile photo of anything but themselves - e.g., almost invariably a toddler, but a vague group photo, a photo of a cartoon, landscape, a flower, their feet, generic artwork, animals, etc., are also par for the course. Very often these individuals don't ever make a peep to you directly after they're let in, and instead enjoy quietly watching what the people on their own friends list do instead. Blowing the image they'd like to project of being "too busy for Facebook," they somehow notice within hours or even minutes after they've been deleted.

Michelle: "Janice is such a Facebook hider. Did it ever occur to her to use a photo of herself WITH her kid as her profile pic?"

Miranda: "Nobody does that! You're crazy."

Facebook hider by TexasAdder September 2, 2010

Facebook Hibernation 

Verb/noun.
1) To reduce the amount of log ins into Facebook.
2) To stop using Facebook for an extended period of time, typically ranging from one month to five months

Joey decided to go into Facebook hibernation.

Because the finals are approaching, Susan decides to go into Facebook hibernation so she would be more committed to and have more time to study for her classes.

Jack Facebook hibernated for nearly two months!

Facebook Hibernation by Zeuskog April 22, 2009