Google and Facebook have been adding gclid and fbclid arguments to outgoing links for a while. Click one of those, and the linked site can conspire with googbook to correlate identities.
More sites could do that.
This is generally better than 3rd partyies because the sites would have to actually conspire, cooperate and trust each other, which is a huge hurdle.
And if the trust is actually there, they could correlate offline without any indication. Facebook already does that (with credit records, likely phone records and medical records as well) and I wouldn’t be surprised if others don’t.
Correlation is less than perfect this way - but e.g. zip, gender and age are enough to give a pretty good correlation, and name makes it almost perfect - if you have an account somewhere, you probably gave these details.
gclid seems to be for adwords only. imo, if you're already the type to click on ads, you shouldn't object to tracking of which site you came from. fbclid on the other hand applies to all links from facebook. it was a major story on HN: https://hn.algolia.com/?query=fbclid
More sites could do that.
This is generally better than 3rd partyies because the sites would have to actually conspire, cooperate and trust each other, which is a huge hurdle.
And if the trust is actually there, they could correlate offline without any indication. Facebook already does that (with credit records, likely phone records and medical records as well) and I wouldn’t be surprised if others don’t.
Correlation is less than perfect this way - but e.g. zip, gender and age are enough to give a pretty good correlation, and name makes it almost perfect - if you have an account somewhere, you probably gave these details.