It is a distinction with a great difference if you can grasp it. To believe there is no G-d requires faith, to not beileve there is a G-d requires no faith. It is faith that we are discussing so please don't say it isn't important to the definition.
To say a discussion on atheism is about faith is like saying not watching birds is a hobby. You are trying to sell a religious way of looking at things to those of us who have no religion. The hairsplitting distinction between 'not believing in X' and 'believing there is no X' is silly for most purposes - see my Santa Claus analogy, if you like - and the main reason I'm an atheist is that I apply the same logic I use for other matters to the existence of supernatural entities.
I know there are non-religious people who make distinctions between being agnostic and atheist, but I'm of the opinion they make this distinction at least in part because of the opprobrium attached to atheism.