The EFF wrote a detailed post about UID2, a proposed way to make it easier for advertisers to identify people via their email.
UID2s will be connected to people, not devices. That means an advertiser who collects UID2 from a website can link it to the UID2s it collects through apps, connected TVs, and connected vehicles belonging to the same person. That’s where the “unified” part of UID2 comes in: it’s supposed to make cross-device tracking as easy as cross-site tracking used to be.
But this will also create new incentives for sites, apps, and connected devices to ask users for their email addresses.
All the more reason to use Sign In with Apple wherever possible or disposable email services.
Check It Out: Behind ‘UID2’, a Way for Advertisers to Track Your Email
“But this will also create new incentives for sites, apps, and connected devices to ask users for their email addresses.”
And all the more reason for me to give them a big FU when they ask.