Originally posted by Steve.Ledger Rules are mean't to be broken. Nothing can move forward if we follow other people's rules all the time.
Experimentation leads to discovery, discovery leads to a new style.
It's the truth. Do what you like.
But the rule is a suggestion because the eyes are good centering point. You'll get enough DoF in the front to put the eyes in focus and enough in the back to keep the back of the head in focus too. If you focus on the nose, the DoF to the front will go to waste and you'll only focus as far back as the eyes, putting the rest of the head out of focus.
The eyes are also a good focusing point on people because they contain a lot of detail. Noses, for instance, do not. If the nose is slightly out of focus, then you won't notice as much as if the eyes are.