Google has been tracking nearly everything you buy

<a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=19942219" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=19942219</a>

and so does every email provider. heck one company even offers you a service to send this data (which they probably use for ad targeting already) to a 3rd party that automates back promotion claims with your credit card or something.