Given that 1 inch is approximately equal to the width of one's thumb, I would have thought that Imperial units are the natural ones to use in this context...
Yes. When I have my phone resting on a flat surface in front of me (say, a bar) I use the outside side of my pinky to scroll. I find it very natural since when my arms are in a neutral position in front of me, my palms are facing inwards and my pinkies are therefore closest to the bar (and the phone).
Also if I am eating a sandwich, my pinkies stay the cleanest.
