Nowadays, many companies are adopting Agile practices, some of them prefer starting with Scrum (I consider it as a mistake because Scrum demands more maturity and knowledge) because of that most of the times (in the best situation) hire a Scrum Master and Product Owner. However, many times they prefer to hire only a Scrum Master (and coach for the same fare ha ha ha) to take care of Agile practices and design a business analyst (or manager which it is worse yet) as a Product Owner.
Secondly, if the company is decided to invest money on Agile, it paid a Scrum training so every member of Scrum Team knows a little of Scrum roles and ceremonies but in a few cases I realized the company invested money to train (and coach as well) the Product Owner which is one of the worse decisions. Why? Because the Product Owner is responsible for the product. In fact, he is acting in behalf of stakeholders (including the sponsors of the project).
I am not in favor of getting Product Owner certification to occupy this role, but each company has to be cautious of the election of this important role in Agile.
Manager and Product Owner?
No, definitely. A few guys are able to forget about his power and assign user stories to each team member or decide by themselves how long will be the project and create a Gantt chart.
I used to work with a good guy but he has not enough temperament to face his manager and say no, I can´t fill in the role of Product Owner because I don’t have the skills and forget to write user stories for Sprint Planning (I had to repeat the Sprint Planning three times in one Sprint because of the PO had never filled in the Sprint backlog with sufficient amount of user stories to work on it).
If your team member or Scrum Master has to chase the Product Owner, repeat the Sprint Planning or listen to him about the lack of time he has to write user stories or refine the backlog. Well, it is a good moment to consider to change your current Product Owner!!!!!