Open Source Software projects that grow strong and well are associated with strong core developer groups, active peripheral communication and high communication interactivity, and external testing groups. In effect, leaders and openness to outside world are the key to success. They are no mere product of wise crowds. In addition, the 80/20 rule reigns supreme. Most projects are run by a small minority that is responsible for a majority of the output.
This is the conclusion of a study of over 200 Sourceforge OSS projects conducted by Singh, Fan, and Tan in 2007.