It's well known that Facebook collects and monetizes all sorts of data on it's uses. Facebook may be a service, but you the user are actually it's product. Facebook may know more about you than your friends and family do. It's goal seems to be to get to know you better than you know yourself.
To this end, many people may not realize that Facebook also follows them elsewhere. In fact, Facebook follows their users' activity on about half of the top 25 sites on the web, incorporating this information into your overall profile.
Perhaps more creepy is this; it was recently revealed that Facebook is spying on you through smart phones and webcams, listening in so as to decipher what music you like to listen to or what movies and TV shows are playing in the background. So if you're home alone one night and get the sense that someone is watching, it's probably not a peeping Tom outside your window, but the one you invited into your home through your computer.
Check out our website for information about teaching kids internet safety.