Here is Facebook's explanation: http://www.facebook.com/privacy/explanation.php#basicinfo http://www.facebook.com/privacy/explanation.php#basicinfo Basically,

Here is Facebook's explanation: http://www.facebook.com/privacy/explanation.php#basicinfo http://www.facebook.com/privacy/explanation.php#basicinfo Basically, if your profile picture were private, it would be hard for someone (who is your friend/acquaintance in real life) who isn't friends with you (on Facebook) already to find you on the site.