Use it when a rapid consensus is required from a team, rather than a more detailed consideration.
Use it when the team is stuck on an issue, for example when they disagree about something.
Use it when the group prefers a structured style of working together.
Use it, rather than Brainstorming, when a limited list of considered opinions is preferred to a long list of wild ideas, or when the group is not sufficiently comfortable together to be open and creative.