Privacy on Facebook is an oxymoron, but that's okay with me. Kind of funny hearing people worry about privacy on Facebook. I think something like Facebook is the last place one would expect privacy. The things I post on Facebook are intended to be shared publicly.
Ironically, something posted on the open web (outside of one's circle of Facebook friends) is likely to have less audience than something posted inside Facebook since Facebook alerts one's friends whenever things are posted. In the 1990s, that process was called "push technology;" a term that seems to have fallen by the wayside more recently.
Something on the open web, such as this blog, is not found as often. People have to surf to the site.
If one is famous, then web sites and blogs get bigger audiences. Otherwise, web sites just get a few Google searches and maybe some friends will look, but most won't bother unless it's brought to their attention. In some cases, the media will notice an obscure web site and bring a bunch of readers; for a while at least. 15 minutes of fame. On Facebook, things are brought to people's attention; at least to the attention of one's friends.
Another worry that some folks might have about posting on the open web is employers who might do Google searches. I guess I'm not that worried about employers because I may not ever look for another job, I'm almost retired. Also, if I was looking for another job, I would want my new employer to accept me for who I am. I share most of who I am and if I'm embarrassed to share something, I hide it from my friends also, or at least I wouldn't potentially broadcast it to all my 260, or so, friends on Facebook.