> You run a merch store. You want to share with your suppliers order data so that you can get the right number of sizes/colors/etc. Is this PII under GDPR rules? Technically, yes! Not only is there information on gender, but also people's height and weight and maybe even family makeup.

That seems like a very long stretch. First of all, why assume that clothes sizes constitute PII at all? The store never asks me for my height, weight or family relations. It asks me what item variants I'd like to order. Even if the item size happens to match me, there's no telling that I'm ordering it for myself. They're just fulfilling an order that's built to my request, not collecting my biometrics. It would have to be an insane world in which "Supplier, send me 20x unisex medium sizes with XYZ illustration" is considered a breach of privacy. Each time the GDPR comes up, there are so many hypotheticals that never happened (and likely can't happen) in the real world, when the much simpler line of reasoning is that privacy regulation is digging too much into the profit motive of corporations and the US at large, so the sore thumb that is the EU needs to be pushed back in line in their minds.

Tracking and ad companies don't need your real name or email to track you across the internet. And even if they did want that, with a large enough corpus of data, a social media company can probably deduce who most people are anyway based on their behavior even if they're technically marked with an "anonymous identifier". Letting business identify you in any way and trade that "anonymized" data back and forth will effectively be a reversal to full tracking.