If I were to pick one word and use that same word as the sole criteria and absolute basis for how well your website is ranked on Google, the word would be relevance. Relevance of a search term to content on a page; relevance as evidenced by link popularity of that page on other web pages on the same website or on other websites and corresponding click throughs from those links; relevance as manifested in behavior of visitors that land on that page; relevance as quantified by click throughs from a website’s search engine results page (SERP) listing. The latter two, has recently recently become even more important to SEO professionals with Google’s personalized search results feature that rolled out in December of 2009.
With Google personalized search, the search results (listings) you see on Google’s SERPs will show you websites that you have actually visited in the past and spent time on because Google has factored in your previous search behavior (your act of searching on Google, clicking a listing and spending time on certain websites, and how often you visit) into the way they rank pages on your search. Google does that automatically, even if you have not activated this feature, but you can actually get search results that does not take into consideration your previous search behavior by clicking the “view customizations link” on the SERP.
So if you are a website owner tracking your rankings or an SEO professional tracking rankings because it is a key metric to gauge results of your SEO activities, then your metrics are skewed or to a graver extent, inaccurate and misleading.
Google is watching what you click on in search results and learns that you like certain sites. For example, if you often search for specific keywords, and on the top 10 organic listings on the next page there is a web page ranked on the number 9 spot, if you click that site and visit that site regularly, or search for the same keywords later or search for related keywords and you end up visiting that same website, over time Google gives that site a boost in rankings, might end up being in the top 3 or even ranked number 1, because it starts to believe that you like that website. But the ranking boost it gets are only for your results you see on your browser, and not for all other searchers and users. In other words if the site is number 1 on the Google listings you see on your browser, it is not number 1 on other users’ browsers especially if those users have not had previous interaction with that website.
So if you are tracking your rankings, if done with the personalized search feature active, you will not get an accurate representation of what your rankings actually are in general for the city/country you are in.
There has also been a question of privacy, “is Google invading your privacy by watching what you are doing and taking note of your behavior on the websites you visit?”
More information about you is actually kept if you are logged into to your Google account while performing these searches, if logged out, there is only limited data that Google collects about you and your behavior, but still it is enough to change what you see on the results page. Below is a table that shows you what they gather if you are logged in or logged out.
So is personalized search bad?
In the aspect of tracking behavior I believe Google to be walking a thin line.. as the char above shows, it appears that by logging in to your Google account, Google takes this as a sign that you allow your behavior and identity to be monitored. But, has Google informed you about this?
Second thing is, as a Search Engine Optimization (SEO) consultant, the biggest concern is keyword rankings of clients might not be credible or accurate, however this can be easily remedied by simply doing the search again without search customizations. Moreover with a better understanding of how personalized search works, SEOs can make adjustments in order to even leverage on personalized search that is active by default, and use that to get that a ranking boost for their websites. I know I have, but if asked how… I am afraid I rather keep this strategy to myself and not make it easily and publicly available.
Reference and Image Source: http://searchengineland.com/google-now-personalizes-everyones-search-results-31195