As the owner of your own website publisher business, or really the owner of any small business you do not have the same job security as people in other fields. The fact of the matter is, small businesses fail, and small Internet businesses do as well. You can insulate yourself from temporary failures of downturns in your revenue by keeping costs low and saving a good deal. However, there are also steps you can take to protect yourself from ever having a downturn.
Every website publisher should have a realistic long term goal in mind when they start a new website. Not every site is going to produce revenue for the long term, some sites by their nature may be limited to a short term existence. To tell these types of sites apart you need to be able to recognize what makes a content site valuable in the long term.
The long term value in a content site is not in its revenue, but in its uniqueness. Specifically in its unique content. People often laugh at the saying "If you build it, they will come." You'll often hear advice from people, including myself, saying that building it isn't enough, you need to market it as well. That's true for new sites, but in this article we're not talking about building new sites but rather maintaining or increasing current website revenue and traffic. So, for an existing website with unique content and established traffic - if you keep building they will keep coming. Once your website is established, so long as it has unique content that you continue to add, the chance of your site failing is extremely slim. The reason is that your site can never be exactly duplicated. Someone can offer similar content, but never the exact same content.
What about sites without unique content? Sites that simply offer mirrors of other sites like Wikipedia or DMOZ? Sites that simply use public domain content? Datafeed driven sites? Well unfortunately a site without unique content can be duplicated. If a site using the exact same content as yours comes along and the owner puts significant energy into promotion then even though you may have established traffic, that traffic could eventually dry up.
The reason why unique content is so important is that with the exact same content you'll rank on the exact same search terms and so the site with better rankings will win. Whereas with unique content while terms may be similar they will never be exact, especially on obscure phrase based searches. That's the crux of it, if your success is dependent on good search engine rankings on a few specific keywords you are extremely vulnerable to competition. You'll also have a harder time retaining visitors since they can get the exact same thing elsewhere.