There’s probably something very profound about this, but we have no idea what it is. According to this thread on the Bungie forum, there have been more kills made in the Halo 3 campaign than there are people alive in the world.
Apparently, Bungie’s calculated that 6,719,996,560 characters have been gunned down in the game, while the estimated population of the earth is 6,705,066,871.
Just goes to show. Not sure what, but it does, doesn’t it?