I am seeing forums on top in most of my niche.From whatever that I have seen so far, Panda loves forums.
It would be wrong to group all UGC sites into one bucket.Article sites are treated differently from forums.
The following seem to be the positives for forums from a panda perspective.
1) unlike article sites, forums are places where people engage more than on other sites.They take time to post their questions, answers and thoughts.It is natural for user engagement to be high in forums.
2) My research also says that forums are not evaluated for things like spelling mistakes or even for duplicate content.The content from many of my pages have been copied to forums (Yahoo answers is one big scraper of my content) and they all are doing fine. Forums could have been exempt from these checks because they are UGC.
3) Since the copied content is only one reply of a thread where many others contribute, the forum thread will act more like an aggregator of content sourced from other sites mixed with user opinion and this will naturally make the forum pages to be lengthy and more detailed.Matt and Amit are on record saying that Panda likes detailed pages and pages with different viewpoints.
In fact, ever since panda happened, I saw google looking for links to forums on two of my pandalized sites.
It is great time to start a forum.
[edited by: indyank at 5:26 pm (utc) on May 16, 2011]