Google is one of the first major search engines to test this new "Personalized Search" technology. This month alone, Google has released a total of 15 new patent applications relating to this new technology.
They have already begun testing many of these new search features in Google's personalized search http://www.google.com/psearch, which is currently in beta test mode.
Because traditional algorithmic search engines have reached a pinnacle, "personalized search" is just a natural, and necessary, progression for Google.
The following is an abstract from one of the Google patents entitled, Systems and methods for analyzing a user's web history http://tinyurl.com/ycdhxl:
A user's prior searching and browsing activities are recorded for subsequent use. A user may examine the user's prior searching and browsing activities in a number of different ways, including indications of the user's prior activities related to advertisements. A set of search results may be modified in accordance with the user's historical activities. The user's activities may be examined to identify a set of preferred locations. The user's set of activities may be shared with one or more other users. The set of preferred locations presented to the user may be enhanced to include the preferred locations of one or more other users. A user's browsing activities may be monitored from one or more different client devices or client application. A user's browsing volume may be graphically displayed.
Basically, what that abstract is saying, is that over time we develop a history of search queries, results that were clicked, advertisements that were click, and a bunch of other browsing activities. Each one of these actions define what our preferences and interests are. Additionally, Google has mentioned that they may begin tracking users instant messaging, word processing, participation in chat rooms, and internet phone calls in later editions.
Within Google's "personalized search", users will be able to access their past search and/or browsing activities to enhance their overall experience. Google is hoping that their past actions will help to define what they are ultimately looking for, or will help to provide a related area of interest. Google's "personalized search" will also allow users create and manage their own profile, which will act in helping define what they are searching for.
Another cool feature, that is sure to have SEO gurus spinning, is that a user's search activites may play a part in the ranking of search results. For example, if a website is visted frequently by a user, it could have it's placement boosted based on the number of times the user has visited before. Google might track how long the user stays at any given website. A site that is bookmarked and visited frequently will almost always rank higher. Now this is great feature if you site gets found and visited frequently by users. But if not, your site might get pushed to the bottom of the barrell for a lesser site that gets more frequent visitors.
What does this mean for you as a webmaster and SEO? It means that your focus should be on quality. In creating your website, you must emphasize visitor optimization and content optimization over search engine optimization.