This is about storing data in the form of "Facebook user XYZ looked at a page about travel to Antarctica" and the reason Facebook wants to store such data is to show them travel offers when they read their Facebook feed?
If so, can I download this data about me? Is there a way to download everything Facebook stores about me and then I will see all the websites and pages I visited that Facebook knows about?
Is that because there are simply not enough GPUs out there to do this at scale?
If so, it will become really interesting once that constraint goes away. There might be a shift in the search space like there was a shift from analog to digital photography.