Judging by the downvotes this is not a legitimate concern? Why?
Talk to anyone who makes money at PPC and they will tell you one thing. You make a campaign, measure the results, change it a little, measure the results, and make incremental improvements to make a profitable campaign.
If you could do that with SEO, SEO would be a lot easier. Google, therefore, has a number of mechanisms (some patented) that cause all hell to break loose if you make the kind of changes to your site that you'd use to incrementally improve it's SEO.
It's one of the reason we are stuck with crappy sites like answers.com, w3schools, and wrongdiagnosis, because once a site like that is successful, the operators are loathe to make any changes lest their rankings drop.