This is from Stanford’s ecorner videos, with the following summary:
Though Randy Komisar, KPCB partner and seasoned entrepreneur, proposes that most successful ventures do not find success in their initial business idea, he still maintains there is value in constructing a thoughtful initial plan. Any “Plan A” must flesh out your business’ assumptions, challenges, and risk mitigation. Those critical first thoughts on paper help the entrepreneur to create a language with which to discuss their strategy and move forward.
If you don’t see the video embedded here, it’s on ecorner.stanford.edu as The Benefits of Mapping Plan A.