You could take inspiration from how Stack Overflow attempts to keep all the answers on the site high quality, it has quite heavy moderation and operates somewhat like a wiki. (It does have a reputation of being pretty newcomer-hostile, though. Being a Q/A site, it also mostly serves as an information dump for Google, so not the best fit for something like Gorilla Gong.)
I would suggest letting everyone contribute (after all, we could run into the exact same problems that were had with vetting contributors), while having those contributions be under some form of approval process. For submitting videos, this could be more lax, just seeing if they are worthwhile machinimas.
Steam's system for curators has worked fairly well, something like that for reviewers wouldn't be a bad idea.