With my website I few individuals got upset as they broke the rules on my message board and then spun off and made there own site. Now I have noticed they are doing a lot of things bad to when it comes to seo techniques. IE key word stuffing, ripping off other sites unique content, Just wondering if google picks up on this kind of thing and will punish sites for this
Sure, just visit Matt Cutts blog (he's a Google employee in charge of spam prevention) and you can read all about it. You can just do a search of his blog or look at the index on the right.
Don't allow posts in your message board until it's approved by you or the site moderator, the approval process will keep the spammers away.
the bad side of the forums is that you will have no control on the content. you can try to approve the replies