bulletin boarder
Someone who posts messages on a bulletin board so frequently/voluminously that it seems like he practically "lives" on the board.
I get so sick of all those notices that come from just a few "prolific posters" in the community, especially if they don't usually have anything very important/valid to say or advertise --- those folks are such shameless bulletin boarders! They don't help themselves or anyone else by putting up so many boring notices... all it does is clutter up the board and draw attention away from the legitimate messages elsewhere on the board.