Text is an efficient medium to express something complex. But the average facebook user is not expressing something complex. He shares quick reactions, emotions, stuff that trigger anger or fun. Not things that requires deep analysis.

For that, video is perfect.

So in the context of Facebook, it makes sense. In the context of ads, it makes sense.

Yes, we don't want to believe it because it sounds like hell to people reading HN religiously, where text is kind, where people debate, where people don't use smileys, and where ideas get evaluated.

But that's not what Facebook is for. And that's not what the people on Facebook want.