For over a year Google has had a personalized search service, which works using techologies similar to Topic Specific PageRank [22 page PDF], biasing search results to boost the relevancy of certain categories.

Recently Google released a personalized home page feature, and an updated version of their personalized search service. The new Google personalized search service will bias search results based upon past search history. Danny Sullivan, explaining the new technology, quoted this:

Personalized Search is an improvement to Google search that orders your search results based on what you’ve searched for before. Learning from your history of searches and search results you’ve clicked on, Personalized Search brings certain results closer to the top when it’s clear they’re most relevant to you.

In October, 2004 Yahoo! launched My Yahoo! Search, which allows users to block or save specific search results.

About a month ago Yahoo! released MindSet. MindSet allows searchers to use a sliding scale to bias search results, making either informational or commercial results more relevant.

Yahoo! recently launched My Web 2.0, which introduced social search features (sharing search results), and allows users to save and tag pages. The Yahoo! Search Blog has more information about the new Yahoo! My Web 2.0 release.

Search personalization is exceptionally important to search marketers. As personalization spreads, the search results will be different for different people, and search traffic will get sliced up. To benefit from search personalization it is crucial to create quality frequently updated content or tools & services people would want to tag, bookmark, and share.