Thread · 4 tweets · 16 Apr 2019

Unless I'm missing something, the page that @katienotopoulos talks about here has nowhere near all the data targeting you on Facebook. It only has audiences built from hashed identifiers. That's a *tiny* fraction of the targeting you're a subject of.

Hashed identifiers are essentially a way for an advertiser to target people on Facebook if Facebook already knows the identifier (eg. an email address) but without revealing it if not known by both parties.

Facebook has A LOT more data that they get from pervasive tracking. Far more ad targeting is driven from that, which is a way more invasive and dangerous practice than hashed matches.

The fact that Facebook reveals advertisers who use the comparatively safer method but keeps those who work through tracking (which gives Facebook much more data, which they can reuse for other purposes) secret always struck me as highly disingenuous.