Earlier quoted context omitted.
>As long as content is hosted on company-controlled servers where ad revenue is the model for survival, you're going to see slow declines and eventual busts like Digg. That's really not what happened at Digg. The problem at Digg was a structure which rewarded "power users" and allowed third party commercial interests to gain control of the site. It's bad enough that Digg had advertising - eventually we were looking a…
Digg failed because of attempts to monetize it better through ads. Users revolted and eventually it crumbled. Users weren't able to control their content. Regarding your second point, if you include Youtube comments, and not just the videos, it's definitely 90% crap.
Comments on youtube... yeah, they're crap for most videos. I guess technically comments are user generated content, but I never really think of them that way. Even more so on a site like youtube where the videos are the important bit.