> The major change here is to stop tracking in anonymous situations (like app installs that won't know which device clicked on an ad and then installed on app), not to stop all data collection.
Let's suppose you use Google or Facebook to discover an e-commerce site, and then you visit that site "anonymously", and then put something in your cart. Maybe you even convert.
If the site has a "log in with {Google,Facebook,etc}" pop-up, then Google/Facebook (even if you do NOT log in) can join your visit with whatever else data they have. (I think Faceboook says, or said, something in their TOS that they won't but I wouldn't trust that-- they're recording the hit to their pop-up after all).
Google / Facebook will already record your click that lead to the site. Now, you might not be logged in to Google or Facebook on the device visiting the third party site, but if anything else on the local network is logged in, then they derive data from your visit even if it's "anonymous." Even the regional impression gives them value.
So here's the deal though: that e-commerce site "owns" that session and impression. At the very least, they paid to serve it. What FLoC and this Android change do is make it harder for Google/Facebook competitor (e.g. Amazon ads, Microsoft, Verizon/Oath, AT&T, etc) from finding something that can join the user visit to whatever data they already have. That makes the impression to the e-commerce site less valuable because now only Google/Facebook can derive data from it.
Moreover, Google / Facebook are going to target ads based upon that visit. Maybe not ads delivered to that user, and maybe not delivered on that e-commerce site (or for them), but they're going to derive targeting value nevertheless. So if the e-commerce site ever wants to run ads, FLoC and this Android setting should in theory make competitors to Google weaker.
So there's a lot of discussion about privacy here, but in the macro I can't help but see FLoC and this Android change as a way to protect Google's monopoly, and Facebook's moat over their own space.
When it comes to mobile, though, I thought there was already so much fragmentation between browsers / quirks, display settings, other User Agent meta, and IP addresses that fingerprinting without cookies was a lot easier than on the Desktop. And by now, many users have transitioned from Desktop to Mobile, making any other previously joined fingerprints more valuable (something Google or Facebook could do, but maybe not ATT/Verizon). So the Android opt-out really only hurts new properties or ad providers who are starting fresh, right?