Fact versus Fantasy

First, a standard disclaimer:

Process is only a second-order effect. The unique people, their feelings and qualities, are more influential.

Scrum practitioners do not report significant variation from the ideals of Scrum compared to its concrete use, presumably due to the relatively small and unambiguous set of practices. The most commonly reported reality checks are the encroachment of non-iteration work on to team members, and attempts by management to direct or organize the team, or solve unasked its problems.

Scrum iterations have also failed when the Scrum Master does not regularly reinforce the project vision and Sprint goals, and the team drifts.