There is an interesting discussion going on in the Google Webmaster Help forums between an old community site that is supposedly heavily moderated and Google. It is long but in summary, it seems like the details are as follows.
This site has been around since the 90s. It is a community site where people ask English questions and others respond and help. The site has done well in Google since maybe before Google was even on the radar. But in mid-November, likely because of the Panda 22 update, that site took a major hit in Google's search results.
John Mueller of Google came in to pinpoint specific pages that have poor quality content and linked the site owner to the official Google Panda advice blog post.
John then goes deeper and talks about the pros and cons of UGC, which he has done many many times. John had a lot of advice but let me pull out one point:
One of the difficulties of running a great website that focuses on UGC is keeping the overall quality upright. Without some level of policing and evaluating the content, most sites are overrun by spam and low-quality content.
The thing is, this site owner said the site is very heavily moderated. He said:
Unless i'm being a 'love-blind' we wouldn't have survived this long (as a community) without a heck of a lot of policing and housekeeping.
He then lists out all the things they do to police and moderate the content and it is a long list.
The interesting part is that DaniWeb, which we've covered before as being hit by Panda also claimed they were hit by this November Panda #22 update as well. Dani posted those details in a different thread. Both this English forum and DaniWeb are huge communities that are supposedly heavily moderated.
So is Panda not working right or are these site's moderation guidelines not working right?
Forum discussion at Google Webmaster Help.