This is why engineers generally don't make good sales people: the desire to tell the whole truth is usually too strong. The world of software is an incredibly dynamic space, so sales and marketing can use a little of that to their advantage. :)
It's impossible to know with 100% accuracy if a great idea will be possible or not. This is one of the reasons why I like the Lean Startup stuff so much, where you can be honest (with yourself, at least) about doing just enough to prove if something is possible/marketable/whatever before investing years and millions into it.
I think you need Guts, wide knowledge and the skill to create synergies at an instant to do this.
Very Ninja!
I always sort of imagined this seat-of-the-pants type behaviour was unique to tiny indie shops & that you grew out of it once you became a 'real business', but I'm sure you'd kick yourself if you blew a big opportunity like that.
Anyway, can we extrapolate from this story and assume that most innovative game studios are geographically situated near vibrantly decorated restaurants?