If you need to get going quickly to ride the wave of a fad before it fizzles, then fast, bare_bones planning may be all you've got time to execute. This works best when you've already got the infrastructure in place, perhaps from previous projects or an established business, and you can simply shift energy and resources to the new idea.
Everyone has prepared a business plan. Well, should that read, everyone should have prepared a business plan? My thinking is that these tend only to be prepared when they are needed, rather than as a useful business tool for all senior management. My top five ingredients are: 1. Understand what a business plan is; 2. Understand what you intend to use it for; 3. Identify and implement the critical steps to achieving a successful business plan; 4. Understand what needs to be included in the plan; 5. Be aware of gaps or weaknesses in your plan.