Do you like having personalized search when you surf the Net?
Google’s personalized or “customized” search has been offered to account holders for awhile. Since December 2009, users who are not signed into a Google account now have the option too. Just select “Web History” at the upper right hand corner of a search results page, and click “Enable customizations based on search activity.” Click again to disable the feature.
What personalized search means to you is that your previously selected pages are more likely to be at the top of your search results the next time you query Google for the same terms or topic. Google offers personalized search to serve more relevant results than a non-human robot program might deliver. For example, without some personal history for guidance, a robot crawler might just as well show you pages about “apple” the fruit when you were searching for computers made by “apple.”
When you choose “enable customizations” and you are not signed into a Google account, Google ‘remembers’ the pages you selected in your past searches through a cookie (a small piece of code) placed on your computer. In this way, Google can use your previous site selections even if you deleted your web searches from your browser.
Of course, this personalization factor makes it more unpredictable for website owners who try to rank higher in searches through generic link building and search engine optimization. It also skews the results for your future searches. This might make your searches more efficient. You may not like it if you value serendipity or more random results.
For more details, John Wieber from www.seomoves.org, provides a nice explanation: Google Personalized Search – Optimization Nightmare or Opportunity