About Negative SEO... I think most people are wrong believing they have been hit by penguin or Panda. In fact, they just lost a link. It often happens with links from forums and blogs as the pages are dynamic. When the link does not appear on a ranked page you lose a huge amount of google juice. You can see the lost backlinks in majesticseo or ahrefs. White hat seos sees 100 incoming domains in webmaster tools and they believe it is a lot but google also count domains with nofollow links and there are also links that are already gone or that said a small fraction of pagerank. If after adding a link to your website from another website... If the webmaster adds also 100 external links to its page, you get then a small fraction of google juice. That's why you may also see a drop in ranking. Negative SEO only happens if google sends a message saying they have found unnatural links to your website.