The author didn't really went into detail. This tournament was the biggest one in history, but not just for Vegas alone. WotC actually set up three tournaments in three cities accross the world (Vegas, Utrecht, Chiba), the same day. Utrecht and Chiba had around 4,000 players each, and Vegas 11,000.

Utrecht was really well organized. It was the first 'pro' tournament I was attending, and everything went quite smoothly. I strongly advise you to do it if you have a chance (especially during those kind of monstruous events, which may be a bit less pro-oriented than usual).