Easy enough. More than half of the people that Facebook recommends to be as "friends" are people whose language I don't speak in countries to which I've never been.
Nice AI, Zuckerbean.
Perhaps having a dense graph is simply more profitable for FB?
Sure they won't know who you know, but they can send their messages (ostensibly "on behalf of") that person you know/friended.
Sure, poison your personal data (get your Fakebook on), but going out and spamming connections may not exactly hurt FB.
No, all I've thought is that the AI sucks and is broken and for a company that's supposed to have the smartest people and unlimited money it should know better.
Beyond that, no.
All of this is of course a designed test to see how accurate the model is, to see how ordering of suggestions influences behavior, to see effects of noise, etc.
They aren't stupid and they aren't bad at their jobs. It's just a test.