I find brainstorming a powerful tool in the Product Manager toolbox and in the Decision Makers' toolbox, in general.
In my view, it is not necessarily the session you read about in many 'brainstorming cookbooks' - first choose the audience, then carefully prepare the questions, everyone can speak their mind freely, list all suggestions, etc. To me, it is actually in its simplest meaning - get some folks together, colleagues or customers, and talk about the issue or the question at hand.
And it's not like we don't practice this already in different ways - a formal meeting, a friendly chat over lunch with few fellas from the office, user groups, advisory boards, UI/UX user testing and so on.
I do see however valuable potential expansion in two directions that is worth to consider - Volume and Scope.
The Volume of the crowd
Fixation and conception are the enemies of any evolution and any revolution, and these are extremely important in tough markets. Freshen up... Don't brainstorm with your usual folks, not your small-favorite milieu, not the close-related group of stakeholders.
Democratize Brainstorming! Why not?
New brains bring innovative ideas, and new eyeballs bring fresh points of view.
The Scope of questions
We are brainstorming when we need help, when we are stuck. We are looking for someone, another person, another brain, another idea, to get us out of a situation.
The Wisdom of Crowds by James Surowiecki has an interesting theory. It basically claims that the collective opinion of a group of individuals has generally been found to be as good as, and often better than, the answer given by any of the individuals within the group.
There for, a good (provocative) question is why not brainstorm about everything? Not just when you are stuck or when no one can give you a straight forward answer.
You can actually already find few examples of companies who started to operate in their day-to-day, based to this theory. As it is pretty common now to do crowdsourcing for QA or Marketing, they do it for Decision Making as well.
Making company-level decisions based on the collective opinion of the company members.
So why in our case, on our product-level decision, shouldn't we ask more 'dramatic' questions and see where this leads? Commoditize Brainstorming!
Two elements are important in brainstorming - the process and the outcome.
The outcome is obviously important as this is where you usually want to end up with, but the process is nothing less.
In the military there is a culture of debriefing. You debrief every event, even if the outcome is pretty much known, or even it was small insignificant one. The process is no less important than the outcome as the system and the individuals need to 'train' for it, be familiar with it and have it in their nature. Something like 'muscle memory' for the way they operate.
Investing in the process and proliferating it will yield more outcomes? better ones? I say, worth trying.