> Certainly it is not in Facebook's interest to allow this kind of data harvesting
Mark Zuckerberg has been quoted through leaked documents to be a strong purveyor of "engagement" at nearly all costs. I don't think giving Facebook the term "accidental" is appropriate anymore. Their desire for engagement trumps the health of their network. I'll dig through my favorited submissions for the WSJ article.
Edit: That was easy: https://archive.md/GQFLq
People are rarely motivated by evil, but they are motivated by opportunity to which an outcome can be perceived as pure evil by the people it affects most.