Paul,
Here's a shot of mine and as you can see I've played with it, but a good example when "thirds" work. The foreground,middle lake and horizon,each share about a third. Obvioulsy, I wasn't thinking "thirds" when I took this, just what "looks best".
Also, since there are TWO dimensions of an image, the "Rule of Thirds" works vertically also,so JC nice shot of an egret(?) on a piling is an example of the thirds rule and that's why it works so well,
Rich