The structure of your website's data is less important than its moderation process. High quality online communities tend to have strong, well-defined moderation policies – Wikipedia and Stack Overflow are good examples, as are HN and certain subreddits (eg AskHistorians).
Regardless of the technology behind a website, online communities without strong moderation tend to die over time as low quality content crowds out everything else.
Regardless of the technology behind a website, online communities without strong moderation tend to die over time as low quality content crowds out everything else.