Google announced December 4th, 2009 a change to how it handles web searches. It has extended the personalized search functions to users who aren't even logged into a Google account. What this means is when you search with Google, it will provide results that are aimed at higher relevancy to you as an individual, as opposed to the average person. It will keep your search history for 180 days.
As an example: If I visit cooking.com often and next week I search for recipes - it may list those pages on cooking.com higher than other sites based on my past browsing history and searches.
Again before this change you had to be logged into to Google for this to take place. Now it is anyone who uses Google. Some think this is a privacy concern and there may be legal issues arise from this eventually. (Remember Microsoft in the hot seat a while back?) Some believe this will actually make the web more useful to visitors. I have preached against people installing Yahoo and Google toolbars for years because of these concerns. You can disable this feature in both scenarios - but historically most users won't be aware of this or won't know how to disable it.
So knowing this, it is important that our websites we serve up to visitors assume this Google feature is turned on. We also know that traffic from Google coming to our websites we host and maintain make up over 83% of the visits - so it is certainly worth paying attention to.
The good news is that in most cases we position our websites for the regional/local customers already which will aid in ranking well on visitor's searches. We also focus on long tail keyword phrases (not just single keywords) which assist visitors finding our websites. Good page design and tracking are still key in placing well in the search engine race.
We will be watching this subject and testing over the next few months to ensure positive results for our clients. In you would like to learn more, view the video below from a couple of the Google engineers explaining how this works.