It’s kept private (supposedly) from people who aren’t friends. But again, friends can divulge that info, often without meaning any harm, and it’s also easy to take a little from FB and search on the web and find out quite a bit more.
Even when a FB page is set to private, it still, for example, shows some of the person’s friends. And if you keep refreshing the page, it cycles through more of the person’s friends. Just this can give info about the person, particularly if they have friended groups, clubs, teams, schools, churches, etc.
But the biggest problem is that once the info is out there, someone else can pass it on, without even thinking of the consequences or your wishes.
I gotcha... Noone knows what the future of Facebook privacy will be.