First and deadliest of all is a founder's unwavering belief that he or she understands who the customers will be, what they need, and how to sell it to them.

Any dispassionate observer would recognize that on Day One, a start-up has no customers, and unless the founder is a true domain expert, he or she can only guess about the customer, problem, and business model.

Founders, presuming they know their customers, assume they know all the features customers need.

Products are sold because they solve a problem or fill a need. Understanding problems and needs involves understanding customers and what makes them tick.

Visionary CEOs don't need someone else to demo the company's key products for them. They deeply understand products, and they have their own coherent and consistent vision of where the industry/business models and customers are today, and where they need to take the company.

The art of entrepreneurship and the science of Customer Development is not just getting out of the building and listening to prospective customers. It's understanding who to listen to and why.