I'm sure if I read a FB page like that and interviewed that poster, I would not want them working for me. We all vent sometimes but if I'm in the mood to disregard professionalism, then I'm not going to make it public. I can't see myself going to the extreme your example went to though, under any circumstances.
That being said, I just recently started on FB but don't think I want people from recent work environments on my page. I keep things set to "friends only" for that reason. It seems like anything written always has the potential to come back and haunt us.
