That was the original Yahoo business model. It doesn't scale. You can't hire enough human beings to curate the entire web, and if you try to automate it, then the SEO spammers can game the automation.
You can enforce penalties (bans for the entire brand/domain/etc) to deter gaming the system, which should take some pressure off the humans which can then focus on the top issues reported by end-users.
It won't be perfect, but at least Pinterest wouldn't be polluting image search for years for example.
