Slightly different approach, but DMOZ – <a href="https://en.wikipedia.org/wiki/DMOZ" rel="nofollow">https://en.wikipedia.org/wiki/DMOZ</a> – was a reasonably big deal back in the day. Imagine Wikipedia but if it were a Yahoo style site directory. It worked reasonably well and was quite tricky to force your way into for a while, but I think it ended up getting overrun in the end.