Flappy Bird had zero Facebook features

Actually, Flappy Bird did have Facebook sharing. And removing it then led to a drop in virality. So, unfortunately, it proves the opposite is true.

But that doesn't mean that slathering Facebook buttons everywhere is unhelpful.

Of course not, but it is unsightly and often unneeded.

I think apps should allow one to individually turn on and off social services.

It did however have a share button after you've died, did it not? Never pressed it, but I'm curious if that helped.