On 1/29/09 Steve Rubel of Micro Persuasion expressed his concerns about Google search engine tracking ability through cookies that they implant on our computers when we use Google Search. Is the Google Cookie Tracking Everyone's Surfing Habits? His concerns:

\"First, Google yesterday made some subtle changes to its privacy policy. Coincidence? Maybe.

Second, according to the Google Adwords blog, the search engine has now added a new site traffic metric in Ad Planner called Unique Visitors (cookies). This, according to Google is a new cookie-based metric that \"help(s) you cross check and compare metrics, similar to Google Analytics unique visitor metrics.\"

The help page goes a little bit further, saying that unique visitors (cookies) is \"the estimated number of unique cookies on a site. The unique visitors (cookies) metric is more similar to data from server logs, analytics applications, and ad servers.\"

Google does not provide any additional details on how they are gathering the data from cookies. Is it possible that this means that as long as you have visited Google once and get cookied that they are now tracking every single site you visit, even if you didn't get there via a search? It's unclear. But it sounds like it. I hope they will be more transparent.

However, if this is true, given the huge number of people that have done at least one Google search (e.g. everyone) that sounds like they are collecting a staggering amount of data. And something that might alarm privacy advocates while at the same time creating the largest consumer panel on the web - e.g. everyone, except those who delete their cookies.\"

Google Response to Steve Rubel 1/30/09: \"A Google spokesperson emailed in the following statement in response to my post...

\"Google does not track users in the manner described in the article. We do not track every site every Google user goes to, nor do we have the capabilities to track in this manner.

The updates to our privacy policy made on Wednesday refer to data collection only for the purpose of detecting and preventing fraud or other misconduct; Google Ad Planner is not using any of this data in our enhanced features. There is no relationship between our updated privacy policy and our updated Ad Planner features.\"

Seems to make sense. However, it doesn't explain where the cookie data comes from. Others point out in the comments that Google has a lot of cookies sprinkled across the web through Doubleclick, etc. and that - in theory - they could triangulate the data.