It depends on who your competitor is. With a large enough budget you could probably take down any site or promote a site for negative kw's. As when Matt Cutts ranked for several bad keywords, a while ago you could just add matt and some random porn kw's and you got his site ranking first.... I think he hand edited the index to disallow his site from ranking for those kw's.
Basically negseo works and Google is lost for as long as they intend to control linking on the WWW, they'll keep messing things up. Links should be freely bought, sold, etc, and the markets should regulate themselves, not the Google Soviet Web.