Think about it in terms of a Venn Diagram with building what users want as a big circle and inside it is a smaller circle labeled success. What you have noticed is that they don't overlap exactly. What does overlap it exactly is a profitable customer acquisition process. That is, if you can find a sustainable advertising channel that has a user acquisition cost less than your average revenue per user, then you win. If you are very very lucky, this process could of course be word-of-mouth. But in most other cases you are going to have to find or engineer a different type of process.<p>Back to the diagram. In the part of the bigger circle that isn't covered by the smaller one are unsuccessful startups that built something users wanted, but still weren't successful. This area can be grouped into traps that companies can fall into. There are many common ones. For example: (a) building something people want, but just not from you, e.g. because there are too many indistinguishable competitors and you don't win the crapshoot; (b) building something people want, but just enough of them to make a lucrative business; (c) building something people want, but they want it for free and other "business models" aren't lucrative enough. There are others too.<p>I have actually been thinking about this for a while, and am writing an in-depth essay on it, including approaches to overcoming it. However, while I was in the middle of it I got side tracked on a new startup idea :). So this is a preview. The short answer is, in my opinion, don't concentrate on "if you build it, they will come", but "if you build it, how will they come?"<p>(And to anyone reading this, I would be interested in feedback on this basic idea. It would help me make my essay better whenever I finish it.)