Having spent a years creating for traditional media, I find the experience of creating non-fiction for YouTube an entirely new challenge. Though production and editing skills come in handy, the requirements of the genre are entirely different - for a wide range of reasons. Almost ever genre appears on YouTube, but in terms of offering audience-friendly documentary video, there are special considerations (Since many vlogs on YouTube are non-fiction by nature, I'll limit my discussion to the documentary form).
First, lengths are short in this world. Though some create (or adapt) longer videos by posting multi-part videos, more effective programs are between 1:30 and 3:00 in length.
Effective YouTube videos offer a means of engagement, usually through the individual creator; in other words, the filmmaker is part of the story - he or she is taking you on a journey. Even if the filmmaker doesn't appear in the video, the audience perceives this as a personal form of expression. YouTube channels maintained by entities (i.e. corporations or comedy groups or otherwise more impersonal entities) can be successful, but are by their nature less engaging.
The technical considerations, for the professional, might seem difficult to accept. Many successful YouTubers have only most rudimentary production skills - what they do have is the will and spirit to create. While many are very interested in improving their game, production-wise, they're also interested in maintaining the ability to express themselves simply and directly. To the YouTube audience, that is most important.
Renetto, whom I've mentioned here before, is a true documentarian in this world, and has developed a large, loyal following over several years on YouTube He now shoots with the HD Cam on his iPhone 4 - he records and comments on his everyday life, including his family and his teenage kids. He's honest, opinionated, and, after having had the chance to speak with him at the "Vidcon" YouTuber's conference a couple of weeks back, I feel he's a true sage of the YouTube community. Another YouTuber, ShayCarl, also records his family's life - he has a younger family, and offers a hipper take on the idea (think the popularity of reality television versus the traditional documentary). He's currently one of the top personalities on YouTube. Both offer a good representation on non-fiction in this genre.
Like everything in the YouTube world, the documentary world here is just taking shape. Though I actually started creating on here with the idea that I was exploring a new world, I've since come to understand that I'm merging my old one, too!