Briefly - a documentary about design briefs

I have recently discovered a documentary created by Bassett & Partners about what a design brief is and how famous people in the design community related to this concept. Famous designers are asked to elaborate on how they define – and use – the brief to deliver exceptional creative results.
Some agree that design briefs are meant to be thought starters and not bound you to strict requirements. Others, mentioned that the simpler the brief the better - simplicity is everything even for a design brief. However, most of the designers interviewed in the documentary agreed that a lot of "briefs" are not briefs at all.
The design brief should stick to being a short form of communication, a tool, an open statement of ambition for the company and it should have a life of its own - it should evolve in time as the design project progresses.
There are designers that do not believe in briefs at all. They believe in relationships where people come together to achieve goals and aspirations. The purpose in this case is to explore the possibilities and be open to unexpected results.
Nevertheless, design briefs will not disappear anytime soon and the Briefly documentary sheds some light on how some awesome designers deal with this.
Designers interviewed: Frank Gehry (Founder Gehry Partner), Yves Béhar (CEO fuseproject), Maira Kalman (Illustrator), John C Jay (President @ GX, Partner @ Wieden + Kennedy), David Rockwell (CEO Rockwell Group), and John Boiler (CEO 72andSunny).