As a photographer, i find this guideline insulting and asinine. You wouldn't tell Van Gogh not to use oil paints because they might pollute the environment, would you? And if you would, you are a fool. Artists of all kinds need to be able to express themselves with different types of media. Besides, digital photos are usually of less quality then their film counterpart, and those that are equally as good are cost prohibitive. I'm sure you can find a way to help the environment without bothering me and my camera.