They obviously exchange (precisely targeted) attention for money: https://www.facebook.com/adsmanager/creation

And they obviously give away some data for free, especially pertaining to users who click through OAuth consent screens as in the Cambridge Analytica case: https://developers.facebook.com/docs/graph-api

What are some examples of transactions where they exchanged data for money?

How does Facebook make money selling data, specifically as it's different than selling ads? I thought their revenue stream was 100% ad-driven.

The corpus of all of your posts are valuable for statistical analysis for ML models, sentiment analysis, and the like.

Isn’t that all to sell you ads?

For the general "you" yes, but not the specific "you". It would be possible to use your data to sell someone else ads.

But they don't? They use data internally to improve ad revenue but I doubt they ever sold data for money or intend to do so.

Do you know what the legal status is of models derived from someone else's data? EG, can I train an AI from every Marvel movie, then use that to produce other movies?

That's not a great analogy because I would be violating other people's IP, whereas FB generally has rights to the data they collect.

Facebook cares about “your” data, but that doesn’t really mean your painstakingly edited review of the new avengers movie. It’s more what you spend time looking at, what you click on, etc.