Photo courtesy imelenchon of Morguefile.com
There's a interesting short article by Jonah Lehrer, author of Imagine: How Creativity Works, that questions the usefulness of group brainstorming. His contention is that ideas generated during brainstorm sessions are not as good as those born out of critique, or individual idea generation and presentation. (I remember participating in critiques in school. It was a truly humbling experience. But, now I understand the incredible value they have added to my career.)
I find this very interesting because I've always suspected that the committee rarely can come up with good ideas. Committee members either aren't trained to critique an idea — especially concerning graphic design or some product innovation — or they try to accept all ideas as good ideas, and come up with nothing of consequence.
This mentality also relates to the popularized crowd-sourcing model. It's the same belief that good ideas come from quantity. "If many ideas can be thrown at the wall, one is bound to be good and innovative."
To be fair, there is a difference between crowd-sourcing and brainstorming sessions. In crowd-sourcing the participants often work on a problem by themselves and present them along with a lot of other people. The downside with this model is that it not only cheats the client out of a genuinely custom solution, it hurts many in the crowd and the design profession as a whole. It's a lot of work for something of little value.