You might have noticed that Youtube made their crappy comment system even worse recently by integrating it with Google+. Vi Hart makes entertaining videos about math, and she's quitting Youtube because of the changes as she mentions on her blog.
http://vihart.com/
Another Youtuber Boogie2988 (you might know him better as his character, Francis) made an impassioned plea to Google to fix the changes because he makes his living off his videos.
I subscribe to other channels on Youtube that have disabled comments. Yes, they were awful before, but now it's trivial to fill up the top comments with absolute garbage. Hopefully something will be done soon.