http://adsense.blogspot.com/2011/05/key-policy-takeaways-from-adsense-in.html If your blog has no comment moderation, then you can be hit with a lot of spammy comments that can impact your AdSense account!
yes, it happened to one of my site which was left to die, with adsense on, and was comment spammed by stupid bots (porn, casino, drugs links, the total!) and adsense disabled ads on, I could have re enabled the ads by cleaning the comment and contacting adsense again, but instead I killed the site and simply made a redirect to another site of mine, just in case there were backlinks left on the web..
this is what akismet plugin is for it will filter many spammy comment with pharmacy,adult,inappropriate terms and reduce the load you can then moderate the rest of comment easily.