I read a good article that explains a few things that could cause an over optimization penalty, the following are the summary of the article.
Know what can cause an over optimization penalty to your site webmasterworld.com/google/4442234⦠#SEO â Danang Probo Sayekti (@danpros) April 22, 2012
What could cause an over optimization penalty:
- Keyword stuffing
- Redirect several domains to one site
- Same / similar anchor in backlinks
- Same Niche same server
- Doorway / thin affiliate
- Link schemes / cheap backlink packages