Product development is a strategic exercise and decisions regarding what functionality to include ultimately impacts the very nature of the organization that builds and maintains the product. In order for the Product Owner to create the Product Backlog for the Scrum team to work on it is necessary to know where each requirement fits into the corporate vision, whether or not there are alternatives that may be better or cheaper, what other projects within the greater enterprise may be similar so as to avoid duplication. Scrum does not take into account any of this, because it is not meant to manage any of these issues. Scrum is meant to support a build and release process; which works fine as long as you know what you are doing before you start.
In order to support the work of the Product Owner you also need a management structure to make the strategic decisions that allow the Product Owner to create a product backlog that will add value to the organization by lowering costs, lowering rework, and producing a product that fits the goals of the enterprise.
In an enterprise that supports Agile the role of Product Owner on a Scrum team might hold the functional role of account manager, project manager, business analyst, engagement manager, but the common set of responsibilities that this functional role manages on a day to day basis involve direct communication with customers, requirements gathering, negotiation with customers and reporting progress to customers on contracted work. In a customer centric management philosophy senior management needs to offer a great deal of support to your Product Owner in the form of clear vision and goals with rules of engagement with the customer group well defined ahead of any requirements gathering or negotiations. If the Product Owner does not have these rules of engagement clearly defined before-hand then the risk is that the enterprise may accept work that it is not able to do, that may take it away from it vision and mission statement, and most importantly that it may cost more than it brings in as revenue. The last risk is difficult for many Product Owners to quantify without help since this involves the entire life-cycle of the product and not just the initial build costs, which are typically the only such costs included in a contracted cost calculation.
In order to support the work of product owners there are tools and techniques available that are well known and well tested and allow them the best possible chance to avoid risk to the project and the enterprise in the process of gathering requirements and addressing the needs of customers.
Supporting the Role of the Product Owner