Martin McDonald carried out a quite interesting experiment on negative SEO and published it on his blog. His target was no less than Matt Cutt’s own blog. The experiment was interesting enough. In fact, the post received “shitloads of social citations, probably quite a few links” in the author’s own words.
More interesting, however, is the interaction involving that particular post. A copy of the post in blackhatworld.com outranked Martin’s original post.(Altogether now. Say “irony”.) And then it apparently disappeared from the index altogether as one commenter stated.
This seems to be fixed now. Searching for a random paragraph in the article only brings up the original article with the copies being omitted.
However, if you look at the omitted results, you’ll see some helpful insight on one of the factors Google uses to rank pages.
Blackhatworld’s copy of Martin’s article got indexed first (in case you missed that).
