Photography is subjective in that what one person may see and like, may look far less pleasing to another person. The Rule Of Thirds is based on what the vast majority see as pleasing, so a shot conforming to it will be seen to be compositionally pleasing to the majority, although some will see it in a different light. It is up to the artist, in this case the photographer, to decide exactly how he or she wants to portray the subject, and to make the most out of the chosen subject. This could mean conforming to the rules where possible, but with the knowledge that sometimes it is better to break or bend the rules a little for a stronger image.