If this seems just a little creepy, consider that you give Facebook a pile of data.  Here is how Facebook describes the advance notice you give them: So don’t worry, Facebook hasn’t installed cameras in your bedroom.  But what they can see, so can your friends.  What and how frequently you post on someone’s timeline might give away that secret flame you’ve been burning for someone even before you change your Facebook relationship status.

     

Facebook knows when you are about to change your relationship status - 30