I voted for private. I can't think of anything I've posted in OT that I would object to the general public seeing that I don't mind NBF members seeing, hell, you are all just a collection of strange internet users to me anyway and the act of signing up to be a NBF member does not in and of itself make someone trustworthy.

Making it private keep the content out of the eyes of the lurkers who'll never sign up. Leave them to lurk the public content of computer subject matter, make OT private and make it well known that it's private, so maybe some of the lurkers will sign up and start to participate.
But if anyone is worried about having posted info in OT that makes them vulnerable if made public shouldn't be posting that kind of info on any web forum in the first place, public or private.