What's the deal with rank?

I just won my first ranked match, then got curious and looked at leaderboards. There's several near the 2 BILLION range. It cuts off at #46 at 500 million, going down to a staggering 3,006. Why the huge difference? I never see anyone in-game past 1,900. 3,000 is hard enough to believe. Where do these numbers come from? If you pull 15 a game like I did, you'd have to play 20 games a day just for 100k in a year. It sounds like hacking.