This post offers a solution on how to get other people out of product management. I see the problem that many people have requirements and desires for the product, but the product manager must be the one planning and prioritising.
However, I disagree with the solution offered. Simply telling people to mind their own business is not sufficient. The product manager relies on input from other departments and should appreciate it, so he needs a more polite way to accept the input and still tell people that after evaluating the request, it might not be fulfilled.