"a question that challenges an entrepreneur to defend, clarify (in very basic terms), or rethink why they do something in their business"
I think that the most productive Start:ME questions fall into one of two basic categories. The first is a question that challenges an entrepreneur to defend, clarify (in very basic terms), or rethink why they do something in their business that has become a passive habit (e.g., why do you attend that same trade show every single year?). The second is a question that challenges the entrepreneur's vision of the future and their concept for how that future can be achieved (e.g., do you want to be selling directly to consumers or via third-party channels? If the former, how will you reach those customers?). Both, in an ideal scenario, lead to either a renewed belief in an existing approach or a revised, clarified view on changes that need to be made.