Even if you set up your own access point, you're still fighting with 500+ other wireless devices in the room for the actual radio waves they all share.
OTOH, maybe they could have asked Moscone Center to use only lower channels for all their wireless access points for visitors, such as 1-8, so Apple could set theirs at 11, now all alone in its frequency range. But they probably didn't know this was going to happen. Oh well, live and learn.
Yeah, who the hell is responsible for all these people carrying around tiny little WiFi devices? Oh. Oops.
Apparently, much of the problem came from people running ad hoc networks and EVDO Wifi hotspots like MiFi and the Sprint Overdrive.