Forum software penalties

[entropytc]

I'm hoping to solicit some feedback on what people feel would be SEO best practices for message board/forum software.  Specifically, while message boards that are healthy can generate tons of unique content, they also can generate a fair share of thin content pages.

These pages include...

• Calendar pages that can have a page for each day of each month for 10 years! (thats like 3650 pages of just links).
• User Profile pages, which depending on your setup can tend to be thin.  The board I work with has 20k registered members, hence 20k user profile pages.
• User lists which can have several hundred pages.

I believe Google is pretty good at understanding what is message board content, but there is still a good chance that one could be penalized for these harmless pages.  Do people feel that the above pages should be noindexed?

Another issue is that of unrelated content.  Many forums have their off-topic areas (the Pub or Hangout or whatever).  On our forum up to 40% of the content is off-topic (when I say content I mean number of post versus raw word count).

What are the advantages and disadvantages of such content?  On one hand they expand the keywords you can rank for.  On the other hand it might generate google organic traffic which you might now want because of a high bounce rate.

Does too much indexable content that is unique dilute your good content?

[PeterM22]

If you a bit of it on a well established site with many highly trusted links, It may have a postive effect. If you did lots of it on a brand new site, It may do more harm than good.