Johnny sells widgets in his niche and builds a nice clean white hat website that due to little competition easily ranks number one. His site remains in number one for years until the one day the competition arrives in the form of MFA's / and the ebay blogs and a couple of genuine competitors with thin low quality websites. Within a few months Johnny and his team are feeling the pinch, his website is now ranking #6, sales have dropped and he's been forced to lay off staff. Johnny has been playing by the rules but he's now forced to hire an SEO company to regain the ranking position he's lost. Another few months pass and Johnny is all smiles because he's back on top, sales are rolling in and business is back on track.
What Johnny does not know is that his link profile is now "manipulated" no longer natural and he's sitting on a time bomb.
Here is the question - How does Google solve this problem without reducing the quality of their own search results. Johnny has the best site, the most relevant website and the best user experience but he's been forced to cheat to keep the doors open. For the sake of this exercise I'm not interested in anything other than search quality, how does Google deal with this mess when just about everyone is gaming the system?