Some people that are new to Scrum believe that the product owner has to be kept at arm’s length. Originally, Scrum books taught that the PO and the development team were separate. I’ve even heard people state that the PO is a chicken, and not as committed as the pigs on the development team. However, according to the latest Scrum Guide, the Scrum team includes the development team, ScrumMaster, and product owner.
Is the product owner part of the team or isolated? Agile principles say that the team should work with business people daily, and the best way to convey information is face-to-face; we also teach that teams ideally are colocated. So in an ideal state, the PO does colocate with the team — if not, he or she still needs to be available to the team on a daily basis, either in person or via other communication methods.
It always depends on the people involved, but many teams are including the PO in sprint retrospectives. If there is a lack of trust between the development team and the PO, then the ScrumMaster has work to do. Everyone should be working together to deliver value, and the best product owners are on the team.