It's never been easy to do a live/interactive quiz for people scattered across various locations. Setting up tele-conferences is not an option, which left conferencing on IM, never a stable and pleasant experience. Wave could well be the answer.
With a group of well-behaved participants (how hard will that be to find at a quiz :-)), a moderator should be able to conduct a quiz with people taking turns to answer. Media files can easily be shared, whether on Wave or elsewhere. Wave seems a natural environment to collaborate like this.