Brainstorming has been a very old & a successful method / path to solve any problem. It actually plays a vital role in derivation for reasoning to any problems. In simple terms, a manual guide to a problem.
Many follow & some disagree to this method. But after using the brainstorming method for a while long now, it has helped to solve problems at faster pace & with valid logic. Brainstorming is a great tool for focus group discussion where in some instances it lasted for days & in some just a day.In the process of brainstorming there are no ideas differentiated as good or bad, its a process where all ideas are considered & decided collectively.
This methodology holistically depends on how an individual or groups start inculcate in their respective fields.
designplay 
My personal experience brainstorming really works, helps especially in crisis time. Multiple ideas come to solve the threats and problems. Recently we arranged a brainstorming session to improve brand marketing offline and online. Lots of ideas, suggestion were coming out from different minds. Some of were out of our boundary and some of really forced us to implement immediately. We applied a method in brainstorming asking for ideas one by one and just note down it. And at last reviewing each idea.
Thanks
Thanks for the comment Atul. True one solution during crisis and also helps for some of the daily activities, if implemented.