So the overall concept of "shove a tracker value into the URL and collate all interactions" makes sense - but how do you track if a user is sharing a URL? Let's say that I'm on a desktop browsing a shopping site. I'm on shopping.site/product/coolthing.html?tracker=12345. I share this with my friend on a mobile device because it looks like something of interest to them. Now how do you handle the other person having th…
Use the referer, is my guess. Whereas browsers are starting to limit the sharing of referers, I don't think there are any plans to limit first party referers. So as long as the referer is your domain, you know the user navigated from within the site. Otherwise, the user followed a link offsite, likely shared by a friend. You can then assign a different tracking id to them.
AFAIK, they are starting to standardize the sharing of referrer. For most people, this is limiting the sharing. However, they used to have an easy to find GUI option to just opt out of referrers in general. That is no longer the case.