Most beginner or intermediate SEOs don’t know exactly what Over-optimization means so I would like to attempt to explain it. There are two types of Over-optimizations; Onsite and offsite.
Onsite Over-optimization: This refers to keyword stuffing or using the targeted keywords too often in your content. Many SEO’s make mistake of writing content only to tweak the search engines not to write good quality for their users. And search engines in particular Google web spam filters can detect that and can cause negative effect on your ranking. The best content is the one that is written for your users. Of course you want to make sure your keywords are there in your content but in a way that makes sense. For example in this post, one of my targeted keywords is SEO over optimization but you don’t see me stuffing my post with that keyword. Just a few times in different forms, a couple times with hyphen and a couple times without embedded naturally in my content. That is good way of putting desired keywords in your content that is both user friendly and search engine friendly.
Offsite Over-optimization: This refer to building too unnatural inbound links growth. You want to make sure you make links in natural fashion. If too many links are made in short period of time, or if too many high quality links are made without having lower key links, or if there are too many links made under too few anchor texts, these are all some of few elements that can raise flags with Google.
Make sure you diversify on your inbound links with different anchor texts so it looks natural. For example if you are doing optimization for a client, let’s say a payday loan lender, then you want to make sure that is not your only keyword you are using. And do not send all links to your homepage. Send a few links with relevant anchor text to inside pages as well for example for the same site, I choose to send payday lender to an inside page with relevant content.
In summary, SEO over-optimization result of poor SEO strategy, and even experienced SEOs have tendency to make that mistake it probably because the get rushed to get faster results either by impatient client or employer. The key is not to give in to that and choose and define an effective SEO strategy that works. Explain things to your clients and your employers and educate them about possible consequence if SEO isn’t done properly. Trust me I know from practical experience!