"But here's why some people probably don't like personalization: It's invisible. There is nothing on the results page that tells you whether your results are personalized or not."

Sorry, this is just not the case: we do provide indication on Google's search results page for personalized results. Here's a couple links that talk about how we surface whether results have been personalized: http://www.google.com/support/websearch/bin/answer.py?answer... is our support page and http://searchengineland.com/google-now-notifies-of-search-cu... is an article on Search Engine Land from 2008 when we started surfacing information on how results were personalized.

Here's a simple demo. Do a search in Chrome incognito mode and go to the bottom of the page. You won't see a link that says "View customizations." Now do a search in regular Chrome and check for that link. When I did a search for [matt cutts] in regular Chrome, I saw the "View customizations" link, clicking the link gives this message:

"Search customization details: matt cutts

When possible, Google will customize your search results based on location and/or recent search activity. Additionally, when you're signed in to your Google Account, you may see even more relevant, useful results based on your web history. The following information was used to improve your search results for matt cutts:

Web HistoryOne or more items in your Web History were used to improve search results. Manage Web History Remove Web History from my Google Account If you're curious, you can see what a search for matt cutts looks like without these improvements. The 'More details' link on your search results page can be used to display this page for approximately 30 minutes, after which it will no longer show this page."

In other words, not only can you tell whether a search results page was personalized, you can click a link right on the search results to see exactly what criteria were used to personalize the results. And that page has a clear link to run the search again without personalization.

As I mentioned before, personalization is typically a minor effect in Google's search results and it's almost always an improvement. But for people who are worried about potential "over-personalization," we do provide easy ways to see when a search was personalized, why it was personalized, and do the search again without personalization.