As Nicholas Carr recently pointed out and as I have mentioned before, there is no one type of “crowd”. He lays out 6 categories: social production, averaging, data mine, networking, transactional, and event.
Each of these “crowds” (and there are surely others) has its own unique characteristics and its own unique strengths and weaknesses. Some crowds, for instance, gain their usefulness from the individual talents of their members. Others (notably the “averaging” sort) gain their usefulness by essentially filtering out those individual talents.
I would also add what I would call a Resource Crowd, which is represented best by crowdfunding platforms such as Kickstarter, Kiva, and IndieGoGo. These platforms aggregate small amounts of money to accomplish a fundraising goal to complete a project. They allow for participation in the funding of projects that might be far out of reach for the average contributor while also providing the funding necessary for a producer that may not have been able to raise funds before such a platform. The power is in the aggregation of small contributions by a large crowd.