Notice how a lot of the answers form a single connected thread: how hard it is to get users, that doing so depends on making what they want, and that to make what they want you have to understand them (instead of working on some idea conceived in a vacuum).
and to understand them you have to observe them, observe the problems they face everyday and create a solution for them so that next time they see you on the street they give you a HUGE hug
Better yet, you need to be one of them. It works well when your service is, well, of service to you! thats when the proximity to the user is maximized.
