I keep seeing google mention user generated spam and tying that in to forums, guestbook pages, or user profiles. We have a forum section on a site, the site is not a forum, just a section. There is no spam, nothing is posted without approval. However I can't help but worry that there may be some tipping point that could be crossed just by having a forum on a site.
Thinking of no-indexing the forum section just to hopefully avoid triggering a flag, if there even is one.
That sounds like you have nothing to worry about. There's nothing inherently wrong with the forum format of content unless of course you don't have a handle on spam. If spam attempts are too much to handle manually, look up "Stop Forum Spam" - that's the name of a plugin I use for SMF and I believe it exists for other forum software as well - works very well.