Every product idea carries four distinct risks that must be addressed during discovery — before committing to expensive delivery work. Cagan argues that most product failures trace back to one or more of these risks being ignored. The four risks form a complete checklist: if you can confidently answer "yes" to all four, the idea is worth building. If any answer is uncertain, that is where discovery effort should focus. Most teams only seriously evaluate one (feasibility) and skip the other three, which is why technically sound products routinely fail in the market.