Quite true that market research is critical. However, the choice of potential markets to research is even more critical. One of the points I read frequently about successful startups is that the founders set out to solve some problem that they had: something that was interesting to them. Doing so gives you an inherent domain expertise - and internal motivator - you wouldn't have otherwise. For instance, I don't have any interest in having a home theater so working on software to control the different components of a home theater leaves me guessing, rather than knowing, what people with home theaters might want.