It's absolutely in Facebook's interest to allow this kind of viral garbage. It feels like engagement, gives people a way to engage socially in seemingly harmless questions. (I'm not at all convinced these are some dastardly data gathering scheme - many of the viral questions don't have meaningful answers.)

It would be so, so simple to stop these. Just de-prioritize posts with too many replies, or replies from people you don't know, or.. anything. The virality of these things sticks out like a sore thumb. Facebook is choosing to not stop them.

Then again as we learned recently Facebook is choosing not to stop all sorts of things on their platform. https://news.ycombinator.com/item?id=28512121