#1. To make sure the formulas do what you expect them to do. Kind of the same
reason that medical students practice on cadavers (ugh) before they take your
appendix out.
#2. That's pretty open. To me, it means telling people where I got the data,
what I did to get in its present format and making sure that people know what
each field means. Sometimes this stuff goes in its own worksheet, sometimes I
use comments. And sometimes, I'll add instructions telling the user to click
on this to run that.
I figure that if the formulas aren't hidden, then the user should be able to
read that formula and see what's going on and trace back to verify the accuracy.
