Why Content is Important for SEO
When site owners get started out with search engine optimization (SEO) they always here that "content is king" or to drive more people to their site they need to write more articles. Not a lot of people explain why they need to do these things or what good comes from it. It's obvious that content speaks a lot about what you have to offer and should convince visitors that you are an expert or that your product/service will solve their problems, but it can also help you gain more traffic. Here's why:
I like to try to only target 1-3 keywords for each page on the site. That means as you build up the list of terms that you are going to go after, you should have a landing page for almost every one. This will help increase conversions because the traffic you get will be targeted to a page that is custom tailed for almost exactly what they are looking for.
Long tail keywords
When working on SEO it's common to focus in on those money keywords that are 2-3 keywords long, highly searched for, but yet highly competitive. However, when you have a bunch of content on your site you can drive visitors with long tail keywords. These are keywords that are low traffic so sites do not concentrate on them specifically. An example would be if you are selling Armani suits and were ranked for "half price black armani suits."
You may ask why worry about them if they are low traffic? First, you aren't going to put any extra effort in. Second, the benefits compound when you get several thousand keywords sending you a few new visitors each month. Third, these long tail keywords typically have a higher conversion rate.
If you notice related long tail keywords that send double digit visitors to your site each month, consider writing an article focusing on that topic.
Authority
Each page that you create adds authority to your site. You need authority just to break into the search engine results (SERPs) and the more you have allows the specific search engines to "trust" your site that much more.
Sculpting Pagerank
Not only does each page on your site add authority, but also pagerank. You can then use that additional pagerank to feed your landing pages by linking to them with the proper keywords in the anchor text. You will really only see the benefits from doing this when you create over 1,000 pages on your site.
With additional pages you can also silo your content to ensure that more of your pages get indexed. A good way to do this is with categories in WordPress. For each of my most popular categories I will create a different menu that is filled with top posts a visitor would want to see if they are interested in that particular category.
Too Much
You don't need to keep typing away until your fingers go raw because you will see diminishing returns. While it's true that each additional page adds value to your site, that value is only added if the page actually gets indexed. If you don't have any links pointing to your site then it doesn't matter if you have 1,000 page, none of them will be in the index so none of them will be able to show up in the SERPs nor add any authority to your site.
Post content at a pace that you can maintain and monitor your webmaster tools to make sure that all of your pages are getting indexed. If your index percentage drops too low, then you need to work on getting more links to your site. The article I wrote on how to get your site indexed faster also applies to getting more your site in the index.