I have had some sites affected as well. I feel that Google has likely identified sites which post articles, whether unique, spun, or duplicate and has lowered the weight they have given these sites in the past, this in turn lowers the weight they give to the links within the articles posted by authors. Many of the sites that I only used article backlinking dropped several hundred pages while other sites that I did a mixture of commenting, article links, and profiles on were either not affected or only slightly affected. By reducing the weight they assign to article links, the less effort webmasters will put into them, thus reducing the amount of content spam.
While this is only a theory, I feel that based on what I have seen Google wants unique content on your site and in what you produce and distribute across the web and definitely no posting duplicate articles around the web.
I remember a time when web directories were all the craze, until Google diminished the value of the links from these directories. Once this value was diminished many webmasters stopped producing them.