Ok this happened to my main marketing site. For years now when we have built sites we have always put our link in the footer of that site where we say designed by and then we always would rotate out putting our company name in or a few different terms that people found us under. About a month ago I get a message in my web master tools that they have noticed some un natural links. So I start looking and I have nothing that would cause a red flag that I can see. Most of my links were from sites that we have built and then from press release with pr web, Chamber of Commerce that we are members of and then sites like yelp, city search and so on. So i responded back and never got an answer. Went to the help forums and submitted my question there and nothing. Well yesterday by chance a person that I know is good friends with a guy that is High up with google in the search Dept. We asked him if he would take a look at my site and tell me why my site lost ranking. He told me its because of the links that are in the footers of the site and that the search engine looks at those as paid links so it doesn't count those links anymore. The reason I got the message of un natural links is some of the sites that I had my link in the footer are rather large sites and its kicking back like 20k from those sites. He would not tell me how long it would take if I took those links off before my ranking came back. But I stayed up last night and all day today removing links off of the 2800 sites that we have done over the past few years. I wanted to see if they have seen this or heard of this causing your site to drop. Once again on this site no link packages were ever done. these are all real natural links and this was the out come of it. Now i have to see how long it takes before my site moves back up.