Robert_Charlton - 9:30 am on Jan 16, 2013 (gmt 0)
Google has repeatedly stated that it is not using Chrome or Toolbar data in the organic search algorithm. For extended discussion about what that might mean, see this thread...
Matt Cutts: Organic Algo Does Not Use Any Chrome Data
Aug 23, 2012
I know that many would like to catch Google with its hand in the cookie jar (pun intended) with regard to Chrome, but I do believe that Google is telling the truth about data from the browser itself.
Most likely, as I suggest in the Chrome Data discussion, they are using cookie tracking, along with a range of other signals as described in Brett's Panda Metric thread (which I reference in the Chrome discussion and am repeating the link here)....
Panda Metric : Google Usage of User Engagement Metrics
April 21, 2011
While Brett speculates about the Google toolbar and Chrome browser, he presents strong cases for multiple other signals. In both threads cited above, aristotle strongly leans toward the Chrome browser. I'm leaning much more toward a combination of signals not native to Chrome, and particularly with cookie-based tracking. Google also has location nailed without browser data, either by ISP data for desktop connections, or geo-tracking on mobile devices.
Another thread here worth checking...
Personalized Search Now Default
There's much to support that use engagement data need not come from Chrome. I agree with TMS's suggestion that a combination of multiple other sources are more likely to give Google a representative picture of searcher behavior than either Chrome or Analytics would.