Searching for Libraries on Facebook

I created a facebook account a few years ago. I found it an exciting and excellent way to keep up with old and new friends. Before Learning 2.0, I had no idea that libraries were utilizing facebook, as well. I searched for libraries using the search engine, and found several. However, all of the sites I found were private, so I would have to add them to my friend list and wait for an approval before I could actually see the site. I understand why personal sites are set to private, however, wasn't quite sure why a library site would set theirs to private...it seems to me that if they kept it unlocked, more people would access their pages.