When you over-optimize your site, you run the risk of falling out of Google’s good graces. Why? Because Google would much rather see a site that is under-optimized than over for one reason:
If you under-optimize, Google just thinks you don’t know what you are doing. Over-optimize and Google thinks you are running a scam. So if you are pushing the envelop of on-page SEO, you are pushing your business towards it’s own fiscal cliff.