David Masover wrote:

>> "If I'd asked people what they wanted, they would have asked for a
>> faster horse." -- attributed to Henry Ford.
> 
> That's actually a really good analogy -- but you see, Ford's leap wasn't 
> abandoning what his clients wanted altogether. People obviously do want cars.

The car industry also did it incrementally. The original "horseless carriages" 
were exactly that - a carriage frame with an engine strapped into the luggage 
rack. Model T cars look square and funny because that carriage was still there, 
underneath.

After people stopped thinking they needed faster horses, and after they 
participated in reviewing the designs of cars, then the horseless carriage 
morphed, feature by feature, into modern cars.

> More importantly, I don't think BDD (or TDD) is about specifying this 
> requirement up-front, nor do they prevent emergent phenomena.

TDD allows you to safely change your design and features while keeping out the 
bugs. That makes just-in-time requirements safer.

-- 
   Phlip