Greetings. There's a widespread belief that has existed for many years, that Google gives or sells user data to advertisers. After all, the ads you see on Google seem to be so relevant! But that's not how it works (and frankly, Google hasn't done as good a job at explaining this in simple terms as one might have hoped).
User data is not shared or sold to advertisers. For example, an advertiser running an ad on Google has nothing to personally identify you (unless you click on an ad to go to their site, then how ever their site operates is in control of course).
How does it work? Let's say it's clear you're searching around on Google for a new power screwdriver. An advertiser somewhere has indicated to Google that they sell tools, including power screwdrivers.
So, Google shows you their ad. Now you know about that advertiser, but they still don't know about you, unless you click on the ad and go to their site, just like any other site.
Obviously at large scale this involves a lot of work, but fundamentally It's really that simple. -L
@lauren Yes. This is particularly maddening in terms of the remarketing systems (the ones that keep giving users the perception that something---Facebook, Google, the Illuminati---is spying on them because they watched a bunch of YouTube videos and now they're seeing Facebook ads for the same topics as those YouTube videos).
I had a front-row seat to the design of DoubleClick's solution to that problem, and I could not explain to the average person how their privacy is protected. I mean literally: *I* don't have the talent to simplify complex concepts (nor memory of enough details to get it right), and *they* don't have the semester of computer science to grasp the tools used (such as zero-knowledge proofs). I know it works---the systems that choose the ad are double-blind so the only place in the universe where enough information collates to display the remarketed ad is the user's client---but the details of *how* it works and *why* it's hard to compromise aren't something I can convey.
... which leaves an (I think justified) mistrust in the mind of the public that the system isn't just doing the simpler solution of spying on them and sharing their private information around behind-the-scenes. I wish Google could take a communication leadership position on this topic, but I see the disincentives to do so. On the other hand, the big incentive *is* there... a sufficiently irritated public calls for these tools to be made illegal.
