A key part to the success of any website is content.  If you are basing the business on traffic then the more content the better.  You can write that content yourself, buy it or you can design a site that causes your users to provide the content for you.

You have likely visited many sites yourself where you are welcome to share and contribute.  Each time someone does, whether it is to vent, rant or console, the site benefits by the addition of more content.  A big factor in all search engine ranking is the number of pages in the site.  If you can leverage the work of others, it can make the difference between having dozens of pages (or hundreds if you are prolific) and having thousands of pages.

Ultimately unless it is completely out of place, think about putting forums on your site.  It is the best way to get contributions without having to invent a new paradigm.  If you are hosting on a dedicated server then you likely have to find the software yourself, but on most shared hosting providers there is already software in place for you to leverage.