They are complicated and change often, even if you think you know them this is a good time to review them.
Think it doesn’t matter? That you don’t care if the whole world sees what you’ve posted? What if Facebook was using your photo in ads? They might be. I came across this blog post today about Facebook could be using your photos in their ads. To change this option –> Settings -> Privacy -> News Feed and Wall -> Facebook Ads -> Appearance in Facebook Ads and click “no one.”
I had no idea this was even an option or possibility and I pay pretty close attention to my facebook privacy settings.
Some additional helpful info on Facebook and privacy: