HWJUU-g5U_I, Negative SEO, Matt Cutts addresses questions about negative SEO.

Learn more about the disavow links feature:
http://support.google.com/webmasters/bin/answer.py?answer=2648487

Have a question? Ask it in our Webmaster Help Forum: http://groups.google.com/a/googleproductforums.com/forum/#!forum/webmasters

More videos: http://www.youtube.com/GoogleWebmasterHelp
Webmaster Central Blog: http://googlewebmastercentral.blogspot.com/
Webmaster Central: http://www.google.com/webmasters/