I can't think of a worse place to look for editorial than YouTube comments. Historically, they've been so bad that YouTube was so users could hear what they had typed before sharing it with the rest of the world.
That hasn't stopped two Firefox developers from coming up with OpinionCloud. This small Firefox add-on will give a video's comments a quick once-over and show you which words are most often used, and the general user sentiment based on a percentage of keywords that are either positive or negative. Clicking on one of the keywords will pull up a list of comments containing that word. All of this appears below the video, and can be toggled on and off.
According to the project page the tool indexed 9 million YouTube comments to help build out its dictionary of slang terms and phrases. And that number is growing each time someone uses it.
Why would you want this? It's helpful on longer videos if you don't have time to sit down to watch them. It also lets you see what people are saying without having to cruise through several pages of comments, which YouTube breaks up to just 10 per page. Of course both of these require users to have commented on the video and left something intelligible, the latter of which you may be hard pressed to find.