traffik_daddy - 2:47 pm on Jan 17, 2013 (gmt 0)
I don't think some of the ranking drops on some of my sites are penalty related, I think it is more a de-indexing of content from other sources which had backlinks pointing to my website. Remove the article from the index and the backlink becomes obsolete, resulting in a ranking drop.
I do a lot of article marketing and noticed significant drops in rank of about 30-40% of my keywords, although not completely disastrous as my quality backlinks are keeping my website ticking over. Time to find more quality backlinks I think.
I could be wrong though (I have been before).