...but execution is hard. It's axiomatic that a bunch of bright people can dream up any number of ideas for startups.
In any venture, however, relentless attention to the details is what separates the real winners from the also-rans.
Remember Startup.com ? The circa 2001 movie about the meteoric crash of govworks.com? At one level it's a dramatic look at an appalling lack of attention to detail when it would've mattered.
How many software companies died on the way to an SaaS model because they did not have the ability to think through the large scale changes a business model shift would require?
I wonder if the commonly accepted overoptimistic forecasting that every business plan seems to incorporate is really rampant optimisim, untested against any kind of comparable or experience base, or if it is a lack of ability to execute - really execute - on the details that make plans work?
When Google Analytics was Urchin there's a great story about how they needed a "Windows" version within three (weekend) days that the engineers said was "impossible." Those same engineers rolled up their sleeves (do t-shirts have sleeves to roll up, really?) and got it done by Monday. It's a legendary story at the company that is now Google Analytics. They won by relentless hard work and attention to detail.
Sometimes that lack of execution is an weak analysis. Everyone starts analyzing a problem by looking at weaknesses and differences. (I'm not the only one, am I?) However, if the next level of action is to jump from the hypotheses being considered to assumptions, a huge mistake gets made. A hypothesis cries out to be tested. Assumptions - no matter how well grounded in experience or "obviousness" are simply a black hole waiting for the entrepreneur to fall into.
Obviously (not an assumption but a fact) a venture succeeds by filling a need in a new and more value added way. The drive to aim higher is basic. It's the well informed use of experimentation - rapidly, learning every step of the way, that makes the difference.