Look for the answers to these questions.
Does the PO have any metrics to look at?
How are they relevant? Money in the bank?
More users?
More leads?
Fewer bugs (reported from in-production systems)?
Only high-value features in the product? Decreasing the code base?
Anyone can cram things into a backlog and a product, endlessly building things that may prove useful or valuable (or not). A successful PO needs to know how to validate their business assumptions, or at least have an idea (put into practice) on how to do a quick and easy validation of business assumptions.
