> Where is the line between optimizing an ad pipeline and violating privacy?

Right at the start.

Of course, the allegation was that Facebook broke privacy laws, and not just that they violated people's privacy, so your response is a total non sequitur: you're talking about how it's good business to violate privacy, which doesn't address at all whether it's good business to break the law, nor whether these laws draw a meaningful boundary.

Unless you meant that anything which is in the business' interest to do shouldn't be illegal for it...?