There was a time when the method of stuffing worked as well on a webpage as it does in a turkey. Back in the early years of search engines, one could easily manipulate a page’s ranking on Google’s SERP  with keyword stuffing.
Sites could rank on a large variety of keywords by simply cluttering them onto a page, even if the keywords were unrelated and the site was absent of any real content.
You could be (somewhat) classy about it by hiding the offending keywords, matching their text color to the background color, or you could just be blatantly obnoxious.
Naturally this led to a terrible user experience, because most people aren’t looking to find a site that just reads “discount bike tires” repeated 500 times. Google and other search engines wised up and began filtering out offending keyword-stuffed pages, because these pages were largely devoid of useful content.
The Dangers of Keyword Stuffing and Over-Optimizing
Keyword stuffing is now considered a strictly black-hat tactic.
Does keyword stuffing work? It depends on who you ask. It does tend to have some positive short-term effects, but it’s playing with fire and rarely is beneficial in the long run. Google will penalize your site if they catch you stuffing the keyword turkey. Your page could be demoted in rankings, or even removed all together!
Google’s own Matt Cutts warned  webmasters about SEO keyword stuffing and over optimization at SXSW last week, saying:
"We are trying to level the playing field a bit. All those people doing, for lack of a better word, over optimization or overly SEO – versus those making great content and a great site. We are trying to make GoogleBot smarter, make our relevance better, and we are also looking for those who abuse it, like too many keywords on a page, or exchange way too many links or go well beyond what you normally expect. We have several engineers on my team working on this right now."
In other words, Google keyword stuffing is a dangerous game, and isn’t likely to get more safe anytime soon.
Google dislikes black hat tactics like SEO keyword stuffing because those methods focus on beating the search engine algorithm rather than a great user experience.
Look at the keyword stuffing example below:
Are you looking for cheap running shoes? If you’re looking for cheap running shoes, look no further. Our cheap running shoes website is the best place to order your new cheap running shoes. Feel free to check out our selection of cheap running shoes from our cheap running shoes selection below.
Pretty unattractive, right? That’s not even the worst keyword stuffing  out there.
The silly thing is, even if you somehow end up on the first page for “cheap running shoes,” no searcher who clicks on to your site will want to stay there. It naturally repels people, like dog poop left out in the sun. No one is going to see that mess and think “Wow, these people really care about me and my need for cheap running shoes.” Instead they will feel disgusted, used, and itching to get out of there.
Keyword Stuffing vs. Responsible Keyword Optimization
It’s essential to differentiate keyword stuffing from general keyword  usage. It’s still really important to use your keyword in your content, so don’t let all this Google will eat your brains and destroy your home if you do keyword stuffing talk frighten you away from responsible keyword insertion.
Like so many things in life, keywords need to be used in moderation. Some other things that rely heavily on moderation:
- Cookie dough: A little bit is like an everlasting gobstopper, too much makes you feel sick. (And could even kill you. Salmonella poisoning anyone?)
- Sunshine: Vitamin D or 3rd degree burn victim? You decide.
Simply focus less on the robo-crawling-spider-bots and focus more on people. You know, the ones who will actually be looking at your site. Create information-rich content that uses keywords appropriately and in the proper, well-to-do fashion. Would Downton Abbey’s Dowager Countess keyword stuff? Not likely. It's simply not done in proper society.
How to Insert Keywords Safely: Walking the Fine Line
So how do you use keyword responsibly?
Some say there is no magic number. Others say there is a magic number: 2-5% keyword density is considered safe by most.
Instead of using the same keyword a hundred and one times, try using some long-tail keyword  variations to spice things up a bit in your content. WordStream has a handy SEO Toolbar  that can help you generate long-tail variations and keep track of how many keywords you’ve inserted to hit that keyword density sweet spot.
Another tip is to try implementing synonyms (various words with the same meaning). Search engines recognize that words like “bat” are homonyms; they are words that have multiple meanings. Google prides itself on relevancy, so they want to be able to differentiate someone searching for a baseball “bat” vs. a flying vampire “bat.” For this reason, there's a database index of Google synonyms  to help it differentiate between word meanings. Google knows that if a site is talking about “clubs” and “bats,” they are probably talking about sports equipment and not flying mammals.
Because synonyms help Google stay relevant, they tend to reward sites that implement them. Having a variety of related words also means that your site is more likely to have crafted content of real value rather than meaningless drivel meant to trick search engines, which gives Google another reason to add weight to synonyms.
What is your experience? Have you ever tried implementing keyword stuffing? Why or why not?