Disney's whole creativity strategy was built around this sort of idea, except they didn't have a Chief Dissent Officer. They made the role of "Critic" an integral part of the creative team.

Um...by definition, the CEO, who sets the company's initiatives (including initiatives to kill other initiatives) and holds the "buck", so to speak, cannot be the chief dissenter, in the same way that the Emperor cannot be the leader of the Rebel Alliance. When Steve Jobs was CEO, the chief dissenter would've been someone who pointed out that the iPhone4 antennae issue should not be glossed over.

I wonder how much consensus Guido van Rossum had when deciding to break backwards compatibility in Python 3. And Mark Shuttleworth when he made Ubuntu this vastly smoothed-over distro, far more than any predecessor.

Ahh yes, he killed the infamous stylus suggestion for the iPad

He also killed Apple's wireless mouse development because he claimed that "nobody wants a wireless mouse." That's why Apple was one of the last to release a wireless mouse.

He was right most of the time, but not all of the time.

He also trashed the Macintosh project until the Lisa bombed, after which he loved it and promptly took it over (making it into Lisa 2 in the process).

That's just one example. Remember that when he returned to Apple, he killed most of the product lines.