A friend of mine just posted this question to me, and my answer to him as follow.
If your company has achieved high maturity level on Agile, i.e. When your company has embraced the spirit of Agile, and that you have enjoy all the benefits Agile can bring to you, you can dominate anybody with proper Scrum knowledge to be your Scrum Master. In those scenarios, the main activities of Scrum Master would be purely facilitating Scrum Ceremonies, remove impediments. Anyone from your existing Scrum team could take turn to play that role.
However, if your company is new to Agile or have some bad experiences in past "Agile" projects. It would be wise for you to engage an experience Scrum Master. Below are tasks that a Scrum Master need to perform, which I copied from Scrum Alliance.
1. "The ScrumMaster is a "servant leader" who helps the rest of the Scrum team follow the process. The ScrumMaster must have a good understanding of the Scrum framework and the ability to train others in its subtleties."
- This task is pretty easy to perform, as long as the person is a Certified Scrum Master, either by Scrum Alliance or Scrum.org, he/she should be ready to perform this task. A good Scrum Master would be able to explain the reason behind each component in the Scrum Framework. This is important for your team to tailor the process components to suit your environment yet still keeping the same value.
2. "The ScrumMaster helps the product owner understand how to create and maintain the product backlog. He or she works with the entire Scrum team to evolve the Definition of Done. The ScrumMaster also works with the development team to find and implement the technical practices needed to get to Done at the end of each sprint."
- This task would require an experience Scrum Master to perform it. First of all, he/she would need to educate the Product Owner, understand business language so that the Product Owner could appreciate why good product backlog is important to the project. The Scrum Master must not take over the creation and maintenance of the product backlog from the Product Owner. After that, the Scrum Master would need to understand the business good enough to guide the Scrum Team on developing the Definition of Done. There are many factors to be considered during this list, as business is always under pressure to deliver, certain technical debt would be unavoidable.
3. "Another responsibility of the ScrumMaster is to remove impediments to the team’s progress. These impediments may be external to the team (such as a lack of support from another team) or internal (such as the product owner not knowing how to properly prepare the product backlog). That said, the ScrumMaster fosters self-organization, meaning that the team itself should remove issues wherever possible."
- To perform this task efficiently, it required high level of people skill. He/She also needs to make intelligent decision on whether an impediment reported should be resolved by the team themselves or the Scrum Master should step in. This is not an easy decision, required a lot of experience to make this important decision right. If the Scrum Master remove all impediments by him/herself, then he/she is taking away the growing opportunity from the team, however if the Scrum Master pushes every impediments back to the team, then he/she is not serving the team right.
4. "The ScrumMaster may facilitate meetings and always acts as a coach for the Scrum team, helping it execute the Scrum process. He or she helps team members work together and learn the Scrum framework, and protects them from both internal and external distractions. The ScrumMaster keeps the Scrum team on track, productive, and growing in ability."
- On this note, one must be able to differentiate between facilitating and taking over.
5. "Ultimately, the ScrumMaster is responsible for ensuring that Scrum is understood and in place, inside the team and outside. He or she helps people outside the team understand the process and the kinds of interactions with the team that are helpful (and those that are not). The ScrumMaster helps everyone improve to make the Scrum team more productive and valuable."
- It is important for Scrum Master to understand the value between each actions in the Scrum Framework. Not to take them by the face value. Every project are unique in the environment and process must be tailored to suit the project.
