Crowd sourcing most definitely provides a lot of opportunities. Allowing multiple users to collaborate on a single work or project allows for new and unheard of ideas to be exchanged, and brings together differing perspectives and viewpoints to help create a more complete and polished final product. At the same time, however, while a number of users are genuinely concerned about the quality of the finished piece and want to make sure it's of quality, just as many people are only in it for selfish reasons. They want to show that their contribution is better than those of the other contributors, and if the collaboration shifts away from their vision or they're not given what they feel is significant credit for their work, they're just as likely to turn on the others, possibly taking measures that can damage the project as a whole.
To provide an example as seen in recent pop culture, a recent chapter in the comic series "Bakuman" featured an artist named Toru Nanamine submitting a manuscript for his comic called "Classroom of Truth" to a magazine for serialization. However, his initial draft, while praised, was passed up. However, Nanamine took unexpected measures by blogging that his manuscript had passed up, uploading scans of it as well, causing multiple angry calls and letters from online readers to the magazine. Furthermore, believing that comic readers knew better than the editorial department, Nanamine's ignored the notes given to him by the editors and instead chose 50 commenters at random and integrated their ideas and suggestions into a newer draft. He would later take this a step further and end up outsourcing much of the art to some of these fans as well.
It proved successful for a short time, but eventually, Nanamine's collaborators became incensed at the fact that he was receiving all the credit for their work, as well as the fact that he was making money off the comic while they didn't receive a cent. In turn, they began to destroy the series from the inside, with some purposefully ruining the art, others dropping the project entirely, a few leaking spoilers about upcoming storylines online, and some even going to the magazine directly and demanding compensation. The scandals and mass exodus of his group's members ultimately ruined "Classroom of Death", as Nanamine's talent alone wasn't enough to maintain the necessary level of quality, and the series was unceremoniously cancelled.
True crowdsourcing will never truly be 100% viable, as humans are selfish beings by nature; at our core, we all want our hard work to be noticed by others. For some, that means trying to outdo and overshadow everyone else so they can't help but look. For others, just getting their name out in the open and letting people know they exist is enough. And a few, of course, just like being disruptive, as negative attention is still attention. Unless everyone involved completely puts aside their own self-centered tendencies and truly believes int he project, focusing 100% on its improvement, there's no 100% guarantee of success with a crowdsourced project. However, that sort of "hivemind" thinking also means the unique perspective each person brings to the table would be held back, ultimately defying the very purpose of crowdsourcing, that being a blend of different views and interpretations to create something unique, and defeating the purpose entirely. As a result, crowdsourcing will likely never be a fully viable option, or at least not for the forseeable future.