This line is causing much anxiety to people on the twitters. So a couple clarifications.
By own I mean, make final decisions and accept responsibility when things go wrong. NOT open Photoshop and do it herself.
The designer is the expert on design, and can give the best advice and design solutions possible. They are like a doctor.
The product managers is the one who will get fired/demoted/miss a bonus if the product doesn’t perform as desired. Consider them the patient.
So the designer’s job is to both inform the product manager of the best possible solutions for the problem they are addressing, and then execute it to the best of his or her ability.
But it is up to the product manager to accept the risk that entails. If he would prefer you “copy google” rather than try your more innovative approach, it’s his call because it’s his ass on the line.
If the designer is affected by consequences of decisions to that same degree — potential loss of job — then the designer could be the owner, but I have never seen this in my life, while I have seen PM’s tanked by arrogant designers.
Your mileage may vary.