Going through Good to Great again, and was struck by Jim Collin's statement that the best companies hire self-disciplined people who don't need to be managed, and the leadership manages the system, not the people.
One of Scrum's principles is that the teams are self-managing. But I can see now that that principle depends on having the right people on the team – disciplined people. Just because I'm running scrum doesn't mean that someone on the team who wasn't previously self-managing or disciplined suddenly becomes disciplined. The opportunity is there for them, and hopefully peers around them to model after, but the brutal facts might be that there are team members who will never become self-managing, self-disciplined. Perhaps the team manages these people off their team, but if the team and process doesn't gel immediately (average of several sprints before typically gelled and consistent), then it is likely the ScrumMaster may be the first to deal with whether a person is right for the team.