Facebookpalm
Like a regular facepalm, but this specific sort must have been provoked by something annoying/cringeworthy/stupid seen on facebook.
"OMG, X just updated his status for the fifth time this hour saying that he's broken up with his girlfriend. Facebookpalm!"
Idiot on facebook: *spouts incomprehensible rubbish*
Everyone reading it: *facebookpalm*
Idiot on facebook: *spouts incomprehensible rubbish*
Everyone reading it: *facebookpalm*