Lean Startup isn't primarily about building things, it's about the process of customer development. To make an analogy, before the advent of the scientific met

Lean Startup isn't primarily about building things, it's about the process of customer development. To make an analogy, before the advent of the scientific method, people would talk about theories, and maybe perform some experiments, but they did not rigorously interrogate the natural world through a cycle of experiments and theories. Some "flaws" in Science one might point out are: "It's all about doing experiments based on hypotheses, but what about discussing theories?" (In practice, scientists do both.) "Science doesn't tell you what hypothesis to test." (True, not directly; you have to build up a model of what past experiments are telling you and get a bit creative.) "If you run five experiments to test five theories, the only thing you can possibly learn is whether one of those five theories is true!" (Also true, to a point, though you might come up with other ideas along the way. Time is finite; you have to choose something test and not test something else.) To rebut the article more directly, it is absolutely in line with Lean Startup to build cheap prototypes, or even build nothing and use humans to run a service at first. It's also necessarily to have a dialogue with the customer, but because of the very point raised in the article that customers don't know what they want until they see it, it is not just a single conversation but a series of conversations over time. As the entrepreneur (like the scientist), you develop hypotheses that you can only test by putting something in front of the customer. When you think of yourself as building the business model, not the product, it becomes even more clear. If a potential customer says, "Heck, I would pay you $X/month just to be able to do ABC," don't take their word for it -- see if you can get them to actually pay for some minimal thing that does ABC, even if it doesn't scale and you are playing Wizard of Oz behind the curtain. That's the spirit of Lean Startup. If they don't make any statements of that form, but you have a strong hunch, then you really need to test it.