I feel for you. The really messed up part is that its the smaller websites that get affected by this the most. A small website with a handful of backlinks, if a competitor buys some stupid "5 million blog comment links" package for that site, it totally ruins their backlink profile and makes google believe they are buying links even if they are not. When google sees 1000 backlinks and 995 of them look un-natural, the 5 legit backlinks mean nothing. Google wants you to believe that they "disregard" any un-natural looking backlinks but that is misleading. I am very passionate about this because I have seen this too many times for it to be coincidence.