when people get on facebook bithing and moaning about something or someone knowing full well that their post will either start a fight or new round of DRAMA.
Dude did you see Niki's post on facebook tearing in to Rachel?
Yeah, I'm tired of her facebitching.
complaining about something that happened to you using your status on facebook. Usually something stupid or irrelevant and no body gives a fuck, hence the "bitching" part.