I'm pretty sure that is a mis-characterization of what actually happened: a 3rd party app collected user profile data from FB _through somebody's friend connection_ [1].

The Zuck then apologized for this undocumented API access leak and FB subsequently patched it out of their platform. It had nothing to do with running ads. We shouldn't let time paper over the details here.

[1] "It also gathered data from their Facebook friends, which reportedly resulted in Kogan having access to the data of millions of Facebook profiles". https://www.cnbc.com/2018/04/10/facebook-cambridge-analytica...

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chihuahua 19 minutes ago | parent [-]

When I was at FB, I worked on a project whose entire goal was to use compiler/type checker technology to prevent intentional and unintentional leaking of personal data in FB back-end code. If you can believe that. The project had a fair amount of resources and high-level support.

I don't know if it was a psy-op or deception campaign or what.

	▲	dehrmann 10 minutes ago \| parent [-]
		I think you're thinking of something else, but they also added "capabilities" to Hack (their main frontend language; it's a PHP fork) to make leaking data between requests or in logs painful.