According to the Facebook FAQ, users may have their ability to send friend requests temporarily disabled if too many of them have gone "unanswered or been marked as unwelcome." I understand this is to prevent spam. But my question is, just what does Facebook consider to be an "unanswered" friend request? When the recipient clicks "Not Now"? When they delete the request? Or do they have to actually mark it as spam?
Also, does anyone know if the number of mutual friends is taken into account?