How sensitive are the decisions you are trying to make to the actual market size? A factor of two? A factor of ten? Does the market exist? Does the need exist?

How sensitive are the decisions you are trying to make to the actual market size? A factor of two? A factor of ten? Does the market exist? Does the need exist? For startups, these last two questions are most useful in my experience: trying to attack a large market because it is well established is not normally a recipe for success unless you have some way to take advantage of a new trend or a new technology. I would also focus much more on what's required for you to reach break even operation in a niche or segment since failure to do so will kill you more quickly than many other things.