Actually, we had a pretty easy-to-use policy regarding which projects are private and which not - if a project included any global financial information (ex. Finance project, Reporting project etc.) or any executive information (Board Meeting, Executive Reporting etc.) we made private.
All the rest projects (Marketing, Program projects, Projects, previously mentioned etc.) were public, even if still in development and even if they included ex. financial info of a certain project. And we added everyone to these projects to share info and gather ideas, but we limited who can edit and who can only comment.