I hate these "photography rules" that are embedded into pictures. Everything and anything should be art, and just because of some made up rules some guy who was going willy nilly made official. If I take a picture of the Niagra Falls but I show too much of the sky, does that mean the picture is ugly, and that Niagra Falls is too? I really hate it man. Number two or one thing I hate about art and its conisseurs.
I know this message was posted a long ass time ago but I just need to point out how ridiculous this post is.
The "everything and anything should be art" approach to art is bullstuff. I guess, of course, anything
can be art but that sure as stuff doesn't mean it's going to be good. Rule of thirds and compositional rules aren't some arbitrary rules that snooty people set because it gets their rocks off, they are factors that legitimately lead to a good looking photograph.
To use your Niagara falls example...

That photo is boring. It's not boring because I said it's boring or because it's breaking some arbitrary rule you set, it's boring because it's boring. It may portray the Niagara Falls which you may think is beautiful, but it's not good photography in and of itself because it's a closely cropped shot in midday and does not capture a particularly striking view of the falls.

This image of the falls is striking, because it A) captures a unique view of the falls and B) follows several rules of photography and art in general, the biggest thing going for it is warm color/cool color contrast between the golden mist and the blue/white of the falls.
Furthermore there is a difference between an ugly photo and a boring/bad photo. Digital cameras have gotten to a point where any photo will be technically good looking, and the only thing you can really do to make a shot ugly is either pick an ugly subject or filter-rape it. The problem ends up being if a photo is boring or poorly composed, or what have you.
Let's look at it in another art form. If I bang on a piano or just kind of make random intervals and weird chords without any real thought or work and say that it's music, does that mean it's good music? Of course not. The rules of music are such that we've discovered what makes a song sound good, and when people write music they adhere to those rules. The same goes for photography, and to suggest that you somehow have a higher understanding of what art is really about than people who have spent their lives learning about art and what makes it good or bad is pretentious and more than a bit wrong.
Of course you're entitled to your own opinion, but to suggest that the rules of what make a photo good are arbitrary/useless is, again, false.