Google pumped out a batch of new videos about webspam via its Webmaster Help YouTube channel. You can find others from the series here.
We just looked at one about the "pure spam" manual action label. This one is about "user-generated spam".
User-generated spam could include forum spam, spammy user profiles, spammy blog comments, spammy guestbook comments, etc.
"The good thing is that normally when you see this kind of message, it normally means that the manual action we've taken is pretty precisely scoped," Cutts says. "If possible, we try to avoid taking action on the whole domain. We might say something like, 'Okay, don't trust this forum. Don't trust this part of the site, and that's kind of nice because it doesn't affect the primary part of your site, as long as your site is high quality. It might just affect your forum. So that's how we try to do it unless we see so many different parts of the site that have been defaced or have been overrun that we end up taking action on the entire site."
The advice if you get this message is basically to clean it up. He suggests looking at new users that have been created, finding the spammy ones and kicking them out of your system. Also, deleting threads that are spammy would be a good idea.
You also want to do preventive maintenance like CAPTCHAs and comment moderation.
Google is clearly doing more to educate people about its manual actions. The company also just put out a new Webmaster Tools feature that lets users see when they have a manual action against them.