Matt, don't Google Toolbar and the Chrome Browser similarly send information to Google for use in improving their services?
Again, if you actually read the article, you will come across the section titled "What About The Google Toolbar & Chrome?" I encourage you to read it.
[edit] Also, see this comment and patio11's subcomment further down the page, both of which were written an hour before yours: http://news.ycombinator.com/item?id=2165469#score_2165578.
I'm pretty positive that's not true. If you run Fiddler when browsing with Chrome you will see constant hits to toolbarqueries.clients.google.com whether you're using Google or not. I could be browsing some MS site and toolbarqueries.clients.google.com gets hit. Chromium doesn't do this.
Edit: You can uncheck everything under privacy and it will still send those requests.
Edit2: What it sends back looks something like this:
<?xml version="1.0" encoding="UTF-8"?><autofillquery clientversion="6.1.1715.1442/en (GGLL)"><form signature="8551191143090325242"><field signature="620769395"/><field signature="2995202485"/><field signature="2175865763"/><field signature="904516291"/><field signature="2953051246"/><field signature="2649047790"/><field signature="2308153337"/><field signature="1003471793"/><field signature="3255484099"/><field signature="1305698505"/><field signature="3676143819"/><field signature="1275502930"/></form></autofillquery>
Looks like auto-fill data, but this happens when I click around a site, NOT when searching Google or typing something in the address bar. For some sites (interestingly, not all) it sends 3 requests for each page load.
and this: http://code.google.com/p/chromium/issues/detail?id=60422
I would guess that Chrome is sending a hash of the <form> (perhaps URL + method?), plus a hash of each of the <input> tags, and Google returns some sort of information about what kind of form it is?
If so, it would mean it's pretty easy for Google to determine which sites you're on from the pattern of hashes sent for each site. e.g. I see this data sent in the clear for pretty much every page on https://www.facebook.com/
From the toolbar privacy policy: "Toolbar's enhanced features, such as PageRank and Sidewiki, operate by sending Google the addresses and other information about sites at the time you visit them."
Google has managed to demonstrate one way MS appears to be using the data. What does google do with their trove of data? That's a lot of data to collect and not do anything with.
If they want to make it perfectly clear they should add into their privacy policies and EULAs.
But the article clearly covers the available public statements on this issue and patio11 dug up a post from Matt Cutts in his comment below that directly addresses this: http://www.mattcutts.com/blog/toolbar-indexing-debunk-post/.