This is all about roles and responsibilities which is often a challenge at technology companies. Even more so as agile development methodologies proliferate.

The role called scrum master is a project management role. This role makes sure the team stays focused on the commitments agreed to for the sprint and removes obstacles in the team's path.

The role you call "product owner" sounds like what I call product manager.

The product manager role is focused on being expert on the market and articulating the market expertise to the rest of the organization so products and services can be built to solve market problems, and then those products can be effectively marketed and sold. A role focused on ensuring product profitability and solving problems people are willing to pay to solve.

The product manager should be providing the boundaries and priorities of what needs to be built, and in working with the development team, will articulate the vision in terms of the market problems to be solved, for which personas, in which market segments. Artifacts can include market requirements, product roadmap, and the product backlog (artifacts to support marketing and sales will include product positioning/messages, and a repeatable sales process). So far, lots to do!

The items in the product backlog need to be prioritized so development works on the most important functionality first. In order to do this well, the product manager needs to spend time in the market, not just in the office.

Which brings me to your question about whether one person can be both scrum master and product owner. If your team has under 10 people, chances are many people are sharing roles (for example product designer/development lead/project manager, QA/level 3 support/release manager, product manager/product marketing manager/sales support, and so on).

Could scrum master and product owner be one person? Sure. But the scrum master is deep into the development process, conducting the daily scrum meetings, keeping tabs on progress of development tasks, clearing obstacles for the team, and possibly jumping into other development tasks as necessary. If the product owner/product manager plays this role, when does she have time to visit the market to make sure the team is building products people actually want to buy? Quantifying opportunities? Gaining in-depth understanding of problems worth solving?

With a tiny team, sharing the role may be a necessity. But as a market-driven practitioner and believer in product management as a strategic role, not just secretary to development, my answer is no. They should be different people.

You may want to read my article on XPM: Extreme Product Management, where I explore the role of product management in an agile environment or one that Steve Johnson wrote, more recently.

Answered by Barbara Nelson