martinibuster - 5:41 pm on Mar 28, 2010 (gmt 0)
Well 1script, every case is different. I don't know how Google found those spam pages, but as far as I know they were not part of the site architecture. In the case outlined above, there was an old chat script on their server, spammers found it, and started making posts on the old chat script.
Links to spam might be harming your rankings but even if they're not, it's a good idea to remove them anyway because that's a bad user experience. Do searches like this to help find the spam:
If your forum is being spammed by bots then introduce a better sign up challenge.