[ChuckMcM]

I don't disagree, but consider that person B is a 45 year old man working for an insurance company he is probably running Windows 10, and Microsoft knows quite a bit about him.

My point is that in my opinion you are over valuing Google's user information advantage. Most purchasing and buying habit information is collected using web page based analytics to an advertiser rather than coming from Google directly.

When Blekko was operating at a consumer search engine we got a great inside look at what tools advertisers have at their disposal to "qualify" their ad bids. If you send the query's source IP to the ad network when you request an ad they match that up with all sorts of cookies and beacons that have fired off that IP address. None of that comes from Google, it comes from all the trackers that are running all over the Internet.

[MarkMc]

Yes, I could be overvaluing Google's access to all that personal data - particularly since I own shares in Google.

I wonder if there is some concrete way to measure that value. For example, imagine if we could find the "revenue per US user per month" for Bing and Google Search (ie. the search engine part of Google). Would that say anything about the value of personal data?