[MauranKilom]

To me, the important parts of (what I would call) brainstorming are "everybody shares the ideas that come to their mind" and "ideas are not evaluated until later". It's happened so many times that some ridiculous-sounding (and outright wrong/unusable idea) has brought us on track to something novel and sound.

"Viability" paints you into a tiny corner of the solution space. Removing it from the equation lets you freely walk around and inspect other corners (which you can paint yourself into later).

[borski]

100%. We've had a few brainstorming sessions, particularly when coming up with new product ideas or features (aside from those customers requested), and while it isn't often that the outlandish idea makes it, sometimes, just sometimes, it does; and sometimes that outlandish idea becomes the most successful part of the company. I've seen it happen at least 3 times. In my opinion, it's one of the few ways to avoid constantly iterating and truly produce something exceptional.