Crowdsourcing is smarter than it appears and must be handled with intelligence. To me, its pros and cons can easily be visualized : think about a coffee break with scores of people in the same room. Some are from your company, friends or relatives, some just joined from the street below. Their only thing in common is to be interested in the conversation taking place. You will get interesting points of views from experts and ignorants, insiders and outsiders, inconvenient truths and convenient hoaxes... a 3D / 360 vision of the topic. Often uncensored (praise informal gatherings and Coffee Break Allmighty). You can be overwhelmed by it quite easily.
Tools will help you sort the mess, but don't rely totally on them either. Beyond your own judgement, trust that of people and experts you trust. Don't rely fully on crowdsourcing, too. That said, crowdsourcing has already become a very valuable strategic intelligence technique, as well as a wonderful marketing tool (to sell all kinds of things, buzz and disinformation included).
(answer to the question "Crowdsourcing: a massive global innovation accelerator or another hype that will fade away?")