A Chatroulette-style platform for video chats with strangers, but with a twist. You connect with 100 strangers, but it only streams audio and video from one at a time, while everyone else is stuck with text chat. Every few minutes, a new person is picked at random and given the "soap box." Use it to rant, show off your new song, or whatever you want.
Other rooms could cater to specific ideas or goals. You could have rooms for debates around hot topics, one for comedians to test new material, one where everyone gets exactly 30 seconds of screen time, and so on.