I didn't bite in lecture but here's my opinion about double-sided pages...
Professor Tantillo said something to the effect of he realized that the grader could just staple a blank sheet at the end of the paper for comments, but this would have an effect on the paper's readablility. We take for granted that we are entitled to good readability, regardless of whether it is good or bad for the environment. How important is readability, or any of the other luxuries that we take for granted? What about saying "driving a hybrid car might be better for the environment, but it won't be as powerful," or "sure I could get by with just using one light, but turning on a second would make the room brighter," or "I could save water by taking a shorter shower, but it wouldn't be as enjoyable" ? They might seem trivial but I really think that all those types of things add up, and at some point it's going to be important for us to take them seriously. Plus, it's not really decreasing your quality of life that much to make small changes like taking shorter showers.
Of course if you start to debate whether hybrid cars are really better for the environment, or if printing single-sided term papers will save grouse, etc. then it gets more complicated. My point is just that we tend to use more than we need, and we're so used to it that we don't realize that what we think are necessities are really luxuries.