[Jtsummers]

They're also useful for small groups, though maybe less useful. They show dependencies between tasks, which tasks can be done concurrently, and which tasks need to be done first, which is useful for organization on every level. It's just that with smaller groups you can (often) get by with almost any approach, even down to just "put a bunch of sticky notes on the wall and take them off when done", trusting that people know the dependencies and priorities.