If your online business banks on Google searches for traffic, then Brendon Scott is a good ally. Scott offers what he and some other search marketers call "negative search engine optimization" or "negative SEO," a harmless-sounding term that amounts to sabotaging a Web site's ranking in search engine results.

Sometimes negative SEO is performed for reputation management, tweaking online content so that it floats to the top search engine results, thereby pushing a critic's negative comments to a lower ranking. But in unusual cases, Scott says, negative SEO involves more nefarious means, convincing Google or Yahoo!'s search algorithms to bury a competitor's site deep within search results, where its traffic practically evaporates.

"I understand the rules of search," Scott says. "And once you understand the rules, you can use them not just constructively, but also destructively. If a new site gains half a million links over the course of a weekend, it looks suspect from Google's point of view. So you make someone look naughty, and then get them caught."

Jason Duke, another SEO practitioner, has this to say: "We don't talk loudly about our clients," he says. "Especially the ones we do morally questionable things for." He intimated he also performs this kind of less objectionable negative SEO when it suits his clients' needs. But he argues that it's a slippery slope from this more accepted tactic to less polite methods of search-rank sabotage.

"SEO can always be seen as good or bad, depending on which side of the fence you're sitting on," he concludes. "That's the reality of search. For every winner, there's also a loser."