This site is currently ranked #1 in Google for Negative SEO. I also noticed that it is ranked at position 1 for SERP Bubbling. The article on negative SEO is one of the most popular articles on the site, and it's popularity appears to be increasing on a monthly basis. I've never been asked to do negative SEO (although I have been asked to remove pages from Google's index from time to time - which you can do in the Google Webmaster Tools). I looked deeper into the stats about who is looking for information on negative SEO, and found that the most common source for referrals come from France.