FB ads engineer here.
Every time I read these threads, I'm
1. Flattered by how sophisticated HN thinks our systems are (they're not. and we're not that smart. FB's A-team stopped working on ads a long time ago)
2. Entertained by how HN thinks ad targeting works (we don't want to know everything about YOU. we want to know basic info about all of our users.)
Hypertargeting doesn't work. Targeting small audiences doesn't provide marketing scale and is extremely expensive. The goal is to have the biggest possible audience, while still applying one or two critical filters. You could hit all 1000 people in a pool for $100 each, or you can hit 1000 people in a pool of 1 million for 50 cents each.
The main priority here is to enable "Show ads to people who own an Oculus" level targeting. This means that people selling VR-adjacent services, products, and content can reliably advertise to their core market without wasting money on non-users. Or maybe they can filter out that segment to show different ads to non-users that convince them to buy their first device. I know most on HN hate any level of targeting, but this has a massive benefit to the VR ecosystem because it allows VR companies to reach their customers much more effectively and sell more products.
FB is actually stripping away features from our targeting system and removing inputs because we spend too much compute power ($$) driving optimizations that don't have any material impact on delivery value. Basic is better. There's no meaningful business value to capturing biometrics or pictures of things in your home. Also, ethics. We do actually think about that a lot these days - it just took us a while to clean up short-sighted product decisions made a decade ago.