There’s a “Goldilocks Principle” as Dr. John Sorflaten describes at Human Factors International. [Link corrected, thanks Kevin]
Goldilocks went into the three bears’ home and tested their chairs, beds and porridge, until she found what for her was “just right” (or so the fairytale goes).
His article fits in very neatly with the theme of my “Leave good enough alone” blog. Go take a read of it there, and find out how to apply the Goldilocks Principle to design.