Wiki is using it to a great extent. Keyword Injection is one of the most important steps in SEO. Here is a brief description if you are wondering what is Keyword Injection. Simply by adding links to keywords in your articles to targeted pages, search engines will rank the targeted page higher for that keyword.

How it works:

Just by linking keywords in your articles or blog to similar targeted pages in your website. For example, your website has a page that list used cars for sale, and you are writing a blog about used cars. Select a few keywords in your article or blog and link them to the targeted page (for example the used car listings page). Use complete links (starting from the http)... This way the links will still work even when others copy your article. Finally, watch your page rank increase overtime.

Benefits:

- When someone is reading your articles, s/he is definitely interested in the subject. They are more likely to click on the link and purchase your services or products.

- Since the keyword is relevant to the targeted page, search engines will relate your page to the keyword which will send better qualified web traffic.

- You'll even get more links when you submit your article or publication to article submission sites. This will yield in higher page rank overtime.

- Most people who copy your article for their site (or use RSS feed to get the article), will include your links and same as above.

This will affirm my opinion that "Good Content" is the most important part of a website. Good content can deliver better business.

Now, let's see some examples on major players who implemented this techniqe and created huge sites. Wikipedia is one of the largest website in the planets and they rank very high for almost any keywords. They did this by making keyword injection very simple for users.

If the user want to link to another subject, they only have to put that brackets [] around the word. Wiki software will find a page related to that keyword and create the link automatically. When the target page is missing, wiki will create an "Add Page" link for users to create that page. Currently, almost every major keyword is linked to a relevant page on Wikipedia that drives more web traffic and increase their page rank.

To create a solution that will automatically link your major keywords to relevant pages in your website, you can create a server script (like PHP or ASP) that have a list of all the major pages in your website with relevant keywords to each. Before the article is published, the script will automatically read your articles for any keywords and link them to your page. Adding such a system can improve your overall site rank (since most of your pages are linked together) and generate better traffic and higher sales.