In the past few years, a new methodology for launching companies, called “the lean start-up,” has begun to replace the old regimen. Traditionally, a venture’s founders would write a business plan, complete with a five-year forecast, use it to raise money, and then go into “stealth mode” to develop their offerings, all without getting much feedback from the people they intended to sell to. Lean start-ups, in contrast, begin by searching for a business model. They test, revise, and discard hypotheses, continually gathering customer feedback and rapidly iterating on and reengineering their products. This strategy greatly reduces the chances that start-ups and corporations will spend a lot of time and money launching products that no one actually will pay for.

http://hbr.org/2013/05/why-the-lean-start-up-changes-everything/ar/1