An entrepreneur needn't be a heart surgeon, but they must have an understanding of the tools a heart surgeon might need. That said, learning a business vertical is the responsibility of a great financier, regardless of its complexity, says Steve Blank, serial entrepreneur. Without this depth of customer understanding - knowing their problems and why they buy - no new venture can succeed. 

Estrin explains how it is important not to confuse marketing with reality. Know when you are marketing and know what is real. Make sure you listen to real customer input, she cautions. 

Verma talks about how the biggest mistake when identifying a market segment is not identifying the customer with the purchasing power. Your original market can be narrow, and will eventually grow, he says, but only if the correct customers are targeted. Find out who is making the final decisions about a purchase. 

In conversation with Stanford's Tina Seelig, KPCB's Randy Komisar points out that while customer feedback is a good idea, it should not be the de facto driver for products and solutions. Too often, consumers miss the mark on inventions (such as ATM's and mobile phones) because they can't conceive that they would ever need them. The smart entrepreneur, says Komisar, asks questions to determine if there is a market need, rather than testing a first-to-market product itself.