What quantity of ground coffee should I use for an automatic drip machine? It seems like a fairly basic question, but there's probably some more science to this. For an automatic-drip coffee machine, how much ground coffee should be used per unit water?

Various sources say that the "industry standard" is 7g (~1 rounded Tbsp) per "cup" (150-175mL, or 5-6 fl.oz.). Is this uniform for any (reasonable) amount of coffee (say, 200mL-4L / 1 cup to 16 cups)? Or would I want, say, a higher ratio of grounds-to-coffee for making 2 cups, than for making 12 cups? I feel like I, personally, tend to use more coffee (per unit water) when making fewer cups (I'm not sure why; shorter extraction time? Matters of water retention? Mere personal preference?). 

Surely this also depends on total extraction time and grind level, but perhaps that is a separate question. With due credit, this question was partly spurred from this recent question.
I think you have already listed the "industry standard" that is the answer to your question.  It is a good starting point for anyone and the amount can be adjusted by taste afterwards (more grounds for stronger coffee, less for weaker).

The amount may vary with brewing method of course, since depending on the method, brew components (grounds, filter, other components) may retain various levels of water. 

The one add on I will stipulate is that it is always better (for groups) to brew coffee that is too strong.  It is very easy to add some hot water to a cup and weaken a cup of coffee,  however, if you like strong coffee and it's been brewed weak, you are just out of luck.