"Conservative Orders of Magnitude" Arguments

I wanted to highlight this one, because as someone who isn't an expert in any of these fields it's an easy one for me to fall for.

My rule of thumb is whenever I find myself applying a fudge-factor of N to a system "to be safe," I should ask myself "why not 10N instead? why not 100N?"

If my only answer is incredulity, I should immediately halt and dump core; my processing has become corrupted.