I propose that teachers from all over the world be allowed to upload videos on to Khan academy in a controlled fashion.
I've been using Khan academy since I watched this talk, videos ranging from how to acquire money for a startup to how stars are born, told in a clear and engaging fashion. However I feel like there could be so much more if people were encouraged to contribute content. Of course it would have to be regulated so that the user wouldn't be flooded with thousands of often subpar videos, but consider the possibilities. New teachers competing to create videos judged on accuracy and popularity would definitely bring new tools to the table, and the efficacy of different videos could easily be monitored by looking at the exercise performance of students watching them.
Once teachers from around the world are brought in on the project they would bring their content, their ideas and their students. The possibilities are immense, but one thing is for certain, despite his wide ranging intelligence, his goodwill and his magnificent teaching skills, Khan cannot build the global classroom alone.