The problem with wifi is that each wireless access point has a shared bandwidth. So with the increasing number of wireless capable devices (phones, laptops, ipods, cameras...) the wireless access points in Disney’s infrastructure become bogged down with people watching videos, uploading pictures from their trip, etc. This is a common occurrence these days now that seemingly every electronic device is fitted with wireless these days. It sounds like their contracted wireless company did build their network with this is mind.
Like other posters said previously, if you have dependencies on wireless, plan to use an alternative.