There is nothing more uncertain that building a product for a market that doesn't exist. When I've lectured to budding entrepreneurs I ask them "What's the most important thing to put in your business plan?" They'll respond with 'cash flow analysis', or 'capital structure', or 'marketing plans'. The correct answer is 'flexibility'. Most startups don't go to market with the product defined in the business plan, for the simple reason that it's impossible to know whether people want the thing you are building until you try to sell it to them. Unfortunately, the developers fall in love with their technology, or the marketers misjudge the market, and the clients don't feel compelled to buy. Getting the right product at the right price requires a lot of trial and error - and a lot of luck. The market will tell you what it wants - if you don't listen it will kick you in the crotch.
