> If so, I would suspect such an identifier is being supplied by the retailer to Facebook for ad targeting. It could also be your credit card issuer, potentiall

> If so, I would suspect such an identifier is being supplied by the retailer to Facebook for ad targeting. It could also be your credit card issuer, potentially. This is the problem, so many companies are harvesting our data now it's almost impossible to know how your personal data is being acquired anymore. That being said, another thing to look out for is sites and apps running Facebook's integration crap. If the e-commerce site in question is running Facebook's code on the site, FB could easily correlate the data (IP address, browser fingerprint, etc.) and connect it back to you even if you are using Private Browsing.