The 7 Deadly Sins of Customer Interviews (And How The Mom Test Fixes Them)

How to Avoid the Most Common Traps That Kill New Ideas

Why do so many startups fail after promising beginnings? Often, it’s not the idea that’s flawed—it’s the way founders seek validation. Rob Fitzpatrick’s The Mom Test identifies seven deadly sins that plague customer interviews and offers a clear path to redemption. Let’s break down these mistakes and see how you can avoid them:

1. Asking Leading Questions: 'Would you use an app that does X?' invites a yes, even when the truth is no. Instead, ask about their past actions: 'How did you handle this last time?'
2. Focusing on Your Idea: When you talk about your solution, people want to be supportive. Shift the spotlight to their experiences and frustrations.
3. Accepting Compliments as Validation: Compliments feel good but mean nothing. If someone says, 'That’s cool,' dig deeper: 'What did you do the last time you faced this problem?'
4. Ignoring Specifics: Vague statements like 'I always struggle with that' are useless. Ask for details: 'Can you tell me about the last time it happened?'
5. Chasing Feature Requests: Customers love to suggest features, but most are distractions. Always ask, 'Why do you want that?' before adding anything to your roadmap.
6. Fearing Tough Questions: The scariest questions are the most important. If you’re afraid to ask, 'Would you pay for this?'—that’s exactly what you need to ask.
7. Failing to Push for Commitments: If every meeting ends with a compliment but no next step, you’re stuck. Real interest means follow-up meetings, introductions, or pre-orders.

Fitzpatrick’s book is full of scripts, frameworks, and memorable examples. For instance, a founder pitching a new productivity tool learns the hard way that polite interest doesn’t equal demand. Only when a potential customer offers to pay or schedules a trial does real validation begin. The Mom Test’s approach is about humility, curiosity, and relentless pursuit of the truth.

By mastering these lessons, you’ll stop wasting time on polite lies and start building something people genuinely want. The Mom Test isn’t just a set of rules—it’s a mindset shift that separates successful founders from the rest.