Google Hell
I've worked with several businesses that were essentially based on driving traffic via search engine optimization (SEO). There are a wide variety of techniques that can be used, but getting high rankings is not easy and highly volatile. I just saw a Forbes article talking about Google Hell - getting placed in the secondary index.
Bottom line - if you are basing your business on high rankings via organic search, there's pretty incredible risk. And the risk is compounded if you are using techniques that are somewhat gray. The best approaches rely on accumulating quality content and quality links and doing minor optimization on top of that solid foundation. It doesn't prevent Google Hell, but it certainly reduces the chances.
Bottom line - if you are basing your business on high rankings via organic search, there's pretty incredible risk. And the risk is compounded if you are using techniques that are somewhat gray. The best approaches rely on accumulating quality content and quality links and doing minor optimization on top of that solid foundation. It doesn't prevent Google Hell, but it certainly reduces the chances.