The principles of the lean startup movement are fantastic: companies should remain small and and validate their market and product as quickly and efficiently as possible.
There are many companies who execute this strategy flawlessly and reap the rewards.
There are also companies that hide behind lean startup philosophy to justify a directionless effort to build a company. Stated plainly, these companies don't have an idea, but test concepts in hopes of landing on something real.
Many people fail to realize that the lean startup movement is still dependent upon VISION.
A company with vision knows their space and has identified an opportunity. They test the opportunity they've identified [the problem] and are able to formulate a solution [their product] based on their interpretation of people's feedback against their domain knowledge [vision]. When their early assumptions are correct, the company only needs to make small corrections to reach their destination. When they're wrong, the company many need to pivot.
A successful pivot is still often directed toward the same broad market opportunity or customer segment -- it's just a change in strategy to reach a similar goal. Someone experienced in the field might say, there's an opportunity in social CRM and I think people need a desktop solution. They may subsequently learn that the correct solution is always on hand and should be mobile based, so they pivot. This is like Columbus heading out to the new world and at least knowing it was "that a way."
A company without vision starts from a place of ignorance and is unable to respond to feedback as it arises. Even if their problem plus solution is only off by a few degrees, they may misinterpret the feedback and pivot wildly. From a distance, these companies are easy to spot because they thrash from idea to idea.
So, you're a prospective startup founder and you've read everything about the lean startup movement. Should you start a company? No, not if you don't understand a market and at least see a broad market opportunity. Lean startup methodologies are just a set of tools to help you achieve your vision.
How do you gain vision? Work in the field or look to your own interests. And if you're unwilling to do that because you just have to start your company now, at least do some serious research before taking any money. Money comes with expectations. When your half-baked idea fails, you'll be forced to come up with something else... which is how you end up pivoting and working on something stupid for several years of your life.
Do yourself a favor, develop some vision before you start your company.