At Supernova 2007, several of us engaged Andrew Keen over his controversial book "The Cult of the Amateur." I will admit to not yet having read the book. Reviews in the blogosphere are scathing, but of course the book is entirely critical of the blogosphere so that's not too unexpected.
However, one of the things Keen said he worries about is what he calls the "scarcity of talent." He believes the existing "professional" media system did a good enough job at encouraging, discovering and promoting the talent that's out there, and so the world doesn't get more than slush with all the new online media. The amount of talent he felt, was very roughly constant.
I presented one interesting counter to this concept. I am from Canada. As you probably know, we excel at Hockey. Per capita certainly, and often on an absolute scale, Canada will beat any other nation in Hockey. This is only in part because of the professional leagues. We all play hockey when we are young, and this has no formal organization. The result is more talented players arise. The same is true for the USA in Baseball but not in Soccer, and so on.
This suggest that however much one might view YouTube as a vaster wasteland of terrible video, the existence of things like YouTube will eventually generate more and better videographers, and the world will be richer for it, at least if the world wants videographers. One could argue this just takes them away from something else but I doubt that accounts for all of it.