Black hat SEO is both a myth and a reality we have to face sooner or later as SEO practitioners. While I abide by probably one of the strictest SEO codes of ethics around and SEO optimize is a clean white hat SEO company itself we still can't deny that there is black hat SEO.
Here some technique of Black hat SEO:
Hidden text – Create modern CSS based websites with JQuery effects. They often hide large portions of text in layers to display them on click or mouse over for usability reasons. Example: CSS pagination.
IP delivery – Offer the proper localized content to those coming from a country specific IP address. Offer the user a choice though. Shopping.com does a great job here.
301 redirects – Redirect outdated pages to the newer versions or your homepage. When moving to a new domain use them of course as well.
Throw Away Domains – Create exact match micro sites for short term popular keywords and abandon them when the trend subsides. Something like tigerwoodssexrehab.com
Cloaking – Hide the heavy Flash animations from Google, show the text-only version optimized for accessibility and findability.
Paid links – Donate for charity, software developers etc. Many of them display links to those who donate.
Keyword stuffing – Tags and folksonomy. Keyword stuff but adding several tags or let your users do the dirty work via UGC tagging (folksonomy) every major social site does that.
Automatically generated keyword pages – Some shopping search engines create pages from each Google search query and assign the appropriate products to each query. You can do that as well if you have enough content.
Mispsellings – Define, correct the misspelled term and/or redirect to the correct version.
Scraping – Create mirrors for popular sites. Offer them to the respective webmasters. Most will be glad to pay less.
Ad only pages – Create all page ads (interstitials) and show them before users see content like many old media do.
Blog spam – Don't spam yourself! Get spammed! Install a WordPress blog without Akismet spam protection. Then create a few posts about Mesothelioma for example, a very profitable keyword. Then let spammers comment spam it or even add posts (via TDO Mini Forms). Last but not least parse the comments for your keyword and outgoing links. If they contain the keyword publish them and remove the outgoing links of course. Bot user generated content so to say.
Duplicate content on multiple domains – Offer your content under a creative Commons License with attribution.
Domain grabbing – Buy old authority domains that failed and revive them instead of putting them on sale.
Fake news – Create real news on official looking sites for real events. You can even do it in print. Works great for all kinds of activism related topics.
Link farm – Create a legit blog network of flagship blogs. A full time pro blogger can manage 3 to 5 high quality blogs by her or himself.
New exploits – Find them and report them, blog about them. You break story and thus you get all the attention and links. Dave Naylor is excellent at it.
Brand jacking – Write a bad review for a brand that has disappointed you or destroys the planet or set up a brand x sucks page and let consumers voice their concerns.
Rogue bots – Spider websites and make their webmasters aware of broken links and other issues. Some people may be thankful enough to link to you.
Hidden affiliate links – In fact hiding affiliate links is good for usability and can be even more ethical than showing them. example.com/ref?id=87233683 is far worse than than just example.com. Also unsuspecting Web users will copy your ad to forums etc. which might break their TOS. The only thing you have to do is disclose the affiliate as such. I prefer to use [ad] (on Twitter for example) or [partner-link] elsewhere. This way you can strip the annoying "ref" ids and achieve full disclosure at the same time.
Doorway pages – Effectively doorway pages could also be called landing pages. The only difference is that doorway pages are worthless crap while landing pages are streamlined to suffice on their own. Common for both is that they are highly optimized for organic search traffic. So instead of making your doorway pages just a place to get skipped optimize them as landing pages and make the users convert right there.
Multiple subdomains – Multiple subdomains for one domain can serve an ethical purpose. Just think blogspot.co or wordpress.com – they create multiple subdomains by UGC. This way they can rank several times for a query. You can offer subdomains to your users as well.
Twitter automation – There is nothing wrong with Twitter automation as long as you don't overdo it. Scheduling and repeating tweets, even automatically tweeting RSS feeds from your or other blogs is perfectly OK as long as the Twitter account has a real person attending it who tweets "manually" as well. Bot accounts can be ethical as well in case they are useful no only for yourself. A bot collecting news about Haiti in the aftermath of the earthquake would be perfectly legit if you ask me.
Deceptive headlines – Tabloids use them all the time, black hat SEO also do. There are ethical use cases for deceptive headlines though. Satire is one of course and humor simply as well. For instance I could end this list with 24 items and declare this post to a list of 30 items anyways. That would be a good laugh. I've done that in the past but in a more humorous post.
Google Bowling – The bad thing about Google bowling is that you hurt sites you don't like. You could reverse that: Reverse Google bowling would mean that you push sites of competitors you like to make those you dislike disappear below. In a way we do that all the time linking out to the competition, the good guys of SEO who then outrank the ugly sites we like a lot less.
Invisible links – You'd never used invisible links on your sites did you? You liar! You have. Most free web counters and statistic tools use them. Statcounter is a good example. So when you embed them on your site you use invisible links.
Different content for search engines than users – Do you use WordPress? Then you have the nofollow attribute added to your comment links. this way the search engine gets different content than the user. He sees and clicks a link. A search bot sees a no trespass sign instead. In white hat SEO it's often called PageRank sculpting. Most social media add ons do that by default.
Hacking sites – While crackers hack sites security experts warn site owners that they vulnerabilities. Both discover the same issues. Recently I got an email by someone who warned me to update my WordPress installation. That was a grand idea I thought.
Slander linkbait – Pulling a Calacanis like "SEO is bullshit" is quite common these days. Why don't do it the other way around? The anti SEO thing doesn't work that good anymore unless you are as famous as Robert Scoble. In contrast a post dealing with "100 Reasons to Love SEO Experts" might strike a chord by now.
Map spam – Instead of faking multiple addresses all over the place just to appear on Google Maps and Local why don't you simply create an affiliate network of real life small business owners with shops and offices who, for a small amount of money, are your representatives there? All they need to do is to collect your mail from Google and potential clients.
