I mean it doesn't matter if its transferred or not, it's the purpose the data is used for.
One concept I've seen floated is separating the advertising markets from the user-facing services. As in DOJ/antitrust legal seperation of Google, Facebook, etc into smaller entities.
In that world Facebook-the-social-network-I-use company would need to send data Facebook-the-advertising-market company for each page load to request some ads to display. What data would be in that request? My reading of EU law is that such data couldn't be personally identifying or of a private nature (so, like, 99.9% of what I do on facebook...). Features like time of day and language of user would be fine and appropriate - the sort of data used by TV networks to choose which ad to display on their broadcast.
It doesn't matter if you seperate the Facebook company this way, my understanding of EU privacy law is that they still can't use your private data to augment the advertising part of the business when you were there to use the social network part of the business. (Note: the social network still provides user aggregation and has value to FB without any ad personalization).
No, Facebook didn't sell them the data... they gave it to them... sort of. CA made a personality test, got users to take the test and grant them permission to use their Facebook data. So users gave CA the data. But, the data users gave CA also included data about their friend graph. CA apparently did not reveal what they were going to do with the data. It was also against Facevook ToS to use the social graph data this way. But CA did it anyway. So Facebook did not sell it to them, they just had an API that have the data away. In the wake of the CA scandel, Facebook shut down parts of their API that allowed this data to be obtained.
CA used a large variety of timewaster Facebook apps (Quizzes and the sort) to gain access to more user data than was likely ever intended, not just about the party that authorized the app, but also about their friends. They essentially extracted the entire social graph including likes and did all their extrapolation from there.
It is more Facebooks inaction despite being aware of this rather than their actions.
I'd like to see an example of an ad platform that actually does this.