On Facebook you can share whatever you want with whomever you want, from a one-to-one conversation, to friends or to everyone.
this from the facebook blog…
While some people want to post to everyone, others have told us that they are more comfortable sharing with a smaller group, like just their friends. We recognize that it is much worse for someone to accidentally share with everyone when they actually meant to share just with friends, compared with the reverse.
So, going forward, when new people join Facebook, the default audience of their first post will be set to Friends. Previously, for most people, it was set to Public.
First time posters will also see a reminder to choose an audience for their first post, and if they don’t make a choice, it will be set to Friends. People can change who they are posting to at any time, and can also change the privacy of their past posts too.
For people already on Facebook, we’ve also received the feedback that they are sometimes worried about sharing something by accident, or sharing with the wrong audience.
Over the next few weeks, we’ll start rolling out a new and expanded privacy checkup tool, which will take people through a few steps to review things like who they’re posting to, which apps they use, and the privacy of key pieces of information on their profile.