[Ghoulish Delight]

I think the other factor is not just the kind of audience, but knowing who your audience is. Even on the larger more "public" message boards we used to inhabit, there was a certain level of confinement. Your posts were unlikely to be seen out of that precise context, and the people coming to see that post explicitly chose to enter that context. Facebook, everything bleeds all over the place, all context bleeds together, there is no separation, you can never feel certain about the eventual audience. It makes it a) difficult to be as open and b) difficult to focus your message.