The Medici Effect by Frans Johansson has some good studies on brainstorming in groups. He cites studies that say that the #1 barrier to innovation in brainsto

The Medici Effect by Frans Johansson has some good studies on brainstorming in groups. He cites studies that say that the #1 barrier to innovation in brainstorming is 'blocking'. Blocking occurs when one person interrupts others, mid-idea. So in order to get the combination of good ideas without blocking, all one needs to do is have a piece of paper per participant, and then one extra piece in the center of a table. Then each participant just writes down one idea (the idea should be on a focused cause ie ideas on fighting spam) and then exchanges his paper with the one in the middle. Then as a participant reads his new sheet, he tries to improve on the idea(s) that are already on the paper before adding a brand new idea. I've tried this and it works for us.