Normally its discussed in the context of a negative seo against a competitor, maybe building thousands of spam links to their site? Something like that.
Negative SEO is often related as Spamming and in short run it may show you result but in long term nooo...Spamming is a big time no
Negative SEO is usually not about spamming a competitor site to get them banned but getting him ranked for "bad" keywords - like michael moore ranked president bush biography first for the keyword "failure"... i think it's not first anymore.
Negative SEO or Reverse SEO is part of Online reputation management. It is about burying your bad reputation in the industry. There are mixed opinion about negative SEO... Some webmasters say that deliberately spoiling your competitor's reputation (for boosting your own ranking) is part of black hat SEO.
Negative SEO are like Black Hat SEO stuff and google are againts it and all your hardwork will be nothing but a file of crap.
You have one web hosting Niche u do getting backlinks from adult theme it is one of negative point and u create irrelavent keywords in original domains .
IMO, negative SEO means deceiving both the user and the search engine. This practice should definitely be avoided.
negative seo is related to off theme. it is nothing but getting more links from other theme with high pr sites it is called Link Spamming Free Recruitment Software