Andreas Gursky's Rhein II, which recently became the most expensive photograph ever, completely ignored the so-called "rule of thirds".
As I was looking at my different "Photo Of The Day" selections (which seem to dominate this Blog since I started posting them) something that I noticed is that I often ignored the rule-of-thirds.
The rule-of-thirds says that a) the main subject should never be in the center of the photograph, but instead should be one-third to the left or right and one-third to the bottom or top of the photograph; and b) the horizon should never be in the center of the photograph, but instead one-third to the top or bottom of the photograph.
While the rule-of-thirds is not a bad idea--and there is a reason so many use it--there becomes a point that the "rule" should be thrown away. If Andreas Gursky had used the rule-of-thirds, his photograph likely would not have sold for over four million dollars.
In other words, don't let photography "rules" get in the way of allowing you to create the best photographs that you can. If the rule-of-thirds works for a particular photograph, use it. If not, then don't use it.