One day some mathematician is going to have a solution that states that we do not exist - then, we'll be in real trouble!
Or....maybe not....since there are an infinite number of parallel universes (and these are infinitely "close" to one another), we might not even notice the loss of a few million. Just by thinking of the possibility, I just killed of a few hundred thousand, and the more I think of it, the more go. And now that you have just read this, a few more hundred thousand just dissappeared. This is turning into genocide.