Q. What types of organizations is the Scrum approach most suitable for?
There is some debate about how suitable the Scrum approach is for what kinds of projects. Generally speaking, Scrum is suitable when project needs might change quickly, and when additional requirements might come up in an unpredictable way. Overall, agile development and Scrum are more suitable when the requirements are less predictable. While the process in itself can scale up to any number of team members, Scrum tends to work better for smaller teams.
It can be argued (but not proved) that the Scrum approach to project management is more natural in the organizations where there is less of a sense of hierarchy and/or authority.