Practitioners of SEO generally have a tendency to lean towards either the light side(building good unique content genuinely) or the dark side(using corrupt and manipulative techniques). BlackHat (dark side) SEO techniques are those that manipulate search engine results and are bent on getting money no matter what happens. It is similar to BlackHat hacking. BlueHat and Whitehat SEO are those that claim to be lawful and samaritans of the web world. This article will focus on some blackhat techniques and the social impact on society as well as their own destruction.

Spammers are one form of blackhat SEO. The massive amounts of emails full of text/html ads in them provide quick revenue for blackhat SEO practitioners. Some techniques involve phishing and making sites strictly for collecting emails. Things such as newsletters and forums have emails attached in their databases allowing blackhats to literally send out thousands of emails within minutes. It is common knowledge that people are plagued with viagra ads in their inboxes daily but do they really sell viagra? People have died in the past due to simple drugs bought over the Internet which were supposed to be sleeping pills.

Many blackhats trade and sell the email lists they've gathered. Some people try to rotate and cycle their emails every once in awhile to avoid all the spam.(Hemanth Dondolu, interview) There are all sorts of invisible information gathering activities on the Internet from these sites. Granted there are genuine statistics being stored but many of them are for purely black marketing. If a user clicks on the ads in the spam email, the blackhat generates referral and clicking revenue. If the user decides to purchase an item, an intermediate step can be taken to simply store that email, password, item and even credit information. Popular auction site Ebay.com owns PayPal.com a third party service that allows users to store money online and link it to their credit cards or bank accounts. If a site were to set up shopping service that used PayPal, an API is readily available from PayPal. The site collects the above information and then forwards it to PayPal's service via a POST such as https://www.paypal.com/cgi-bin/webscr[options](PayPal, API doc). However, nothing is stopping this site from storing that information and then reselling it or using it for other purposes. By simply doing a whois on a domain name, you can retrieve the address, phone number and name of the individual who registered that domain. It is illegal by law to forge your registration.

Search engines such as Google evaluate the popularity and relevancy of a site based on the number of backlinks (Page, Lawrence, et. al.). However many believe that natural link building is more effective and natural than suddenly having 1000 links to the website over one night. One person got banned from Google adsense program because a popular site Digg.com who keeps the latest news articles online had this person's article on the front page(Adam mckerlie). The article was so popular that all that traffic hit his page. This sudden spike in traffic caused Google to flag the site and take it down as bot traffic. This was a genuine mistake on Google's part since that traffic was legitimate and not robot generated from something like a botnet (a bunch of hijacked computers to run commands issued by the person who compromised it). This can also be applied to backlinks. Too many backlinks too fast flags search engines to watch it more carefully. Where these links come from also matter.

Yahoo! and Google provide a way to check the competition's links. Simply typing "link: yoursite.com" will post the results of who is linking to yoursite.com(Google, Webmaster tools). Google however, limits the results to approximately 100 links. There are several other backlink checking networks that will post many more results. As Aaron Matthew Wall mentions, it just doesn't depend on who links to you, but who you link to as well. Search engines can tell a lot about the type of people sites link to. This can positively or negatively affect the page popularity. If for example, a site with a high PR were to link to yoursite.com, this is considered a quality link and getting a few of these would boost traffic immensely to yoursite.com. The page with high PR has a greater PR value to distribute when it links to another page. Linking to another page is essentially casting a "vote" to increase the PR value of the page it linked to. (Wall, whole page)

One such example of reciprocol linking (that is yoursite.com links to external sites and external sites link back) shows how each page has a PR value to distribute equally and that in turn can help increase the PR of yoursite.com's One such example of reciprocol linking (that is yoursite.com links to external sites and external sites link back) shows how each page has a PR value to distribute equally and that in turn can help increase the PR of yoursite.com's index page. From Ian Roger's Page Rank site: Each arrow represents a link.

With this in mind, blackhats have developed whole linking networks called link farms(Wall, pg.99). Basically these web pages offer the exchanging of links to increase PR value. The only issue here is that pages who submit to these services generally increase the PR of the service page more than their own. Blackhats can choose to do whatever they want with the linking. So yoursite.com may properly link to linkfarm.com but linkfarm.com has so many links that it may have to cycle links; that is a link to yoursite.com is randomly generated on a page once in awhile so it is not permanent. The consequence of this is that when search engines like Google do a crawl, yoursite.com's link might not be viewed at all. New people looking to develop links to their networks typically fall into this trap and since the PR value of linkfarm.com gets higher, it will most likely be found earlier on the search engines. One must be very careful in choosing who links to yoursite.com and what links go out. The more relevant the link, the better. If a site about remote control cars was linking to a ceiling fan site, that would be deemed irrelevant and not add much value to the remote control cars site.

It should be noted that the purchasing of links can be highly effective if done right and done naturally. Some search engines implement the idea of a nofollow noindex tag in the hyperlink tag. For example, external site. The nofollow and noindex tell the search engine to not follow the link to the external site and the noindex part tells the search engine to not even mark the link in its cache. These rules can also be applied to a whole directory via a robots.txt file which tell the search engine robots not to index and follow links the directory. These link farms can appear to have yoursite.com permanently on but the vote is never cast if the search engine never sees it. These link farm techniques can be particularly detrimental to businesses and entrepreneurs seeking to expand their web presence on the Internet.

More often than not, these blackhat techniques do work but they only work short term(Wall, aggressive seo section). Unique, relevant and links from quality sites that relate to yoursite.com have a much better long term value than these blackhat techniques. While the search engines do try their best to filter these websites out, the rate at which these sites get built are much faster than the search engines can screen. Once the site is banned, the blackhat would have already moved onto another. Many website traffics are largely from search engines, with all these ads, parked pages and link network sites in the way it depreciates the quality content that the web can produce.