The problem is that people could be insincere, non-rational or ignorant. I doubt they will know what their problems are, what they are willing to pay or what the solution could be. There's a great quote by Henry Ford: "If I had asked people what they wanted, they would have said faster horses."

For Nathan his pain point could be something related to writing and publishing books. I think this would be a much better problem domain since he is a user and I am sure he has some problems regarding this process that could be improved.