Is it possible to go too far with your SEO efforts and over-optimize your site? Yes, it absolutely is. In the early days of the internet, some over-optimization techniques could help you rank well in search results. But the search algorithms have become refined enough that they account for spammy tactics and you’re much more likely to get penalized for over-optimization, so avoid going too far with your SEO.
This Yoast blog article addresses the most common form of over-optimization: keyword stuffing.
Top Hat Rank Blog
Arsen at Top Hat Rank goes into detail about over-optimizing and keyword stuffing, definitely something to avoid.
SEO for Publishers Webinar
What SEO over-optimization looks like and how to properly optimize your pages instead.
Search Engine Journal
The history of keyword stuffing and how it’s treated by Google now.