Search engine optimization can sometimes be divided into two broad categories: “black hat” and “white hat.” Black hat optimization is the kind that exploits in a negative way loopholes and technicalities in search engine processes to get a higher results rank.
Examples of black hat optimization include word stuffing, and the use of link farms that illegitimately draw people to a web site. For this reason, it is sometimes referred to as “spamdexing.”
Black hat methods attempt to fool search engines into thinking that a site is relevant and legitimate to the search words, when in fact there may be no real relationship at all.
Black hat SEO can be effective for a short amount of time, especially if the goal is simply getting page hits. However, in the long run it is an efficient method to use. Black hat tactics dilute the significance of keywords and create a negative experience for customers who want to find relevant search results but instead come across useless web sites.
Because of this, today’s search engines are now sophisticated enough to identify sites that use black hat methods over time and delist them from their results page. Extreme cases can even get sites permanently avoided. Users that come across sites using this method can report the site directly to the search engine.
People looking to increase hits on their site should use legitimate “white hat” tactics which not only increase traffic over time but also make the internet a more useful and interesting tool.
For more information, see https://www.google.com/webmasters/tools/spamreport?hl=en