A WebmasterWorld thread has discussion around Google now telling you how the search results were either customized based on your previous searches or personalized based on your web history. This is not all that new, relative to search, Danny wrote about it at the end of July.
Let me just catch you up quickly. Search for pizza st louis and then search again for just pizza and you still should get customized results for St Louis. Here is a screen capture:
Yes, it says, "Customized based on recent search activity. More details." When you click on the "more details" link you are taken to an explanation page:
Google has several types of pages like this, explaining how the results were customized or personalized based on your location, previous searches or web history.
In fact, Bryan Horling, Software Engineer, Personalized Search was on the Personalized & Customized Search at the SMX East conference, where Danny and him went back and forth on those features. So for a detailed explanation on this stuff, check out that session coverage.
Forum discussion at WebmasterWorld.