Most sites that can be said to have natural SEO are those that are classified as informational sites. Informational sites can be money-making monsters as it is your clients that supply most of the keyworded copy that ends up in your Q and A sections, forums and other places on your site.
The most successful informational site include magnet content authored by experts (and search engine optimized professionally if need be), a means of collaborating with another equally big or bigger site and most importantly --powerful facilities for allowing users to contribute content. After all it is crucial to the success of your site to have your web visitors constantly adding their own thoughts to your site, which in turn are then crawled by the search engine spiders and indexed as new content.
However one problem with an informational site with natural SEO is that it can become hard to manage over time. You need a means of moderating the site and also a way of identifying and eliminating problematic members of your online community who may be supplying irrelevant content or even hijacking your business.
Managing this type of site comes down to choosing the right web host. You need to choose one that will allow you to keep a database of users, keep track of who looked at your site and at exactly what and keep track of which users are costing you the most time and money with little payback. You might also need to buy software to keep track of how users are coming into the site and which external links they are selecting (clickthroughs) and keep track of which advertisers' banner ads have been served and to whom and whether or not they were effective. This type of vigilance is typical of a successful SEO maintenance program to keep an informational community operating at its smoothest.