The Harvard Business Review says they have proof that Henry Ford never said “If I had asked people what they wanted, they would have said faster horses.” It’s an interesting piece, but it’s the conclusion I want to quote here:

The real lesson learned was not that Ford’s failure was one of not listening to his customers, but of his refusal to continuously test his vision against reality, which led to the Ford Motor Company’s failure of continuous innovation, resulting in a catastrophic loss of market share from which it never recovered.

Translation: regardless of where your innovative ideas come from, make sure you test those ideas with users and learn from their feedback.

The iPhone might have been one man’s vision, but the way users interacted with the first generation iPhone paved the way for the iPad and the iPhone 4. They tested their vision with a real product, and then learned from it.