Here's an article from the Stanford Social Innovation Review entitled "The New Volunteer Workforce":
In this article, the authors talk about the poor management of volunteers by nonprofits. In fact, more than one-third of volunteers in one year will not return the following year. Some great nuggets in this article.
We have to rethink completely our volunteer management model - a change to a 'volunteer engagement' model. Our volunteers expect more, demand more, and should be given more. A wealth of talent and expertise, at an incredibly cost-effective level, totally wasted due to inefficient and dated techniques.