&gt; how many real-world businesses could benefit from the same type of invasive tracking ... we don&#x27;t allow that sort of privacy violation in our actual lives.<p>We do, but apparently many even on HN don&#x27;t realize it. Brick and mortar stores track customers through their phone signals (providing unique identifiers and location), cameras that can track where people go in the store and even what they look at, and more. Here are a couple of good resources where I&#x27;ve learned about it (though they cover much more than those issues):<p>* <a href="http:&#x2F;&#x2F;www.mediapost.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.mediapost.com&#x2F;</a><p>* <a href="http:&#x2F;&#x2F;www.iab.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.iab.com&#x2F;</a>