Sep Kamvar from the Personalized Search Team at Google has the post on the Google Blog about the launch of Google's personalized search.
Sep Kamvar has posted a list of his publications, including a short paper with an overview of some techniques for personalized search called "An Analytical Comparison of Approaches to Personalizing PageRank". Note that one of the co-authors of this paper is Glen Jeh. Glen Jeh was lead author on the "Scaling Personalized Web Search" paper that describe the technology behind Kaltix, the personalized search company acquired by Google about two years ago. It seems all roads lead back to Kaltix.
After seeing Sep's post, I have to say that I am in awe of the boldness of this rollout. Google isn't just sticking their personalized search in a corner of Google Labs. No, as long as you enable Google's My Search History feature (which is off by default), every search you do at google.com is personalized. Wow, very cool, and surprisingly aggressive.
As for the feature itself, it's a little hard to tell. First of all, not all searches are personalized. I tried a search for "news" which was not personalized. I tried another search for "personalized search" and that was personalized. How could I tell? The only indication is a subtle link on the right upper corner of the page that says, "Turn off Personalized Search for these results". Clicking that link yields a page with what appears to be the same search results in a very slightly different order, items moved up or down by just one or two positions.
It's fine to be subtle, but this might be a bit too subtle. Unlike Findory, there is no indication of which search results are personalized. Unlike Findory, there is no explanation of why a search result was reranked. It seems confusing. It basically says, "Don't look at what we're doing. Just trust us. We'll make your search better. Don't worry your pretty little head about it."
The problem with this is that, as good as personalization is, it isn't perfect. When you make a mistake -- and you will make mistakes -- it's important to explain to users why you did what you did and give them a way to fix it. Both Amazon and Findory explain why they made a recommendation and give users an opportunity to change the personalization.
It is possible that Google doesn't explain their recommendations because they can't. Only some techniques for personalization are able to easily provide clear explanations. If Google is using the subject-based Kaltix techniques, for example, it would be difficult to provide explanations, since they would be using completely different relevance ranks from the generic search.
Regardless, I am amazed and impressed by Google's aggressive move into personalized search. Personalized search is the future, and Google just took one giant leap forward. Yahoo, MSN, Ask, and AOL suddenly look to be far, far behind.
See also my post from earlier today, "A real personalized search from Google".