An intentional status update in the wee small hours of the
night, giving the impression that the poster is sleep facebooking or away with the fairies. It's actual intent is for just a handful of people to understand, to encrypt a message or for humor. Corruption of 'status' and 'it's late, as'
"Hahaaha, did you see Seth's been sleepfacebooking at 2.30 again?" "nah bro, he was sending a Slatus Update to his gfriend"