I once wrote about how one possible way to make money off YouTube was to add some call-to-action interaction to the last frame of the clip; this space is currently occupied by the promos for related videos. A new start-up called Involver has brought this model to life:
"Involver’s unique vision is to provide more than just “video with a buy button”, creating a tool for marketers that does more than deliver millions of impressions with no way to capture the audience. The platform uses a rich set of video plug-ins to allow the campaign owner to capture email, offer quizes or surveys, even take orders or donations - all within the framework of the video, never forcing the viewer to browse to a new Web page." (-- StageTwo).
You can post Involver-powered videos to a whole bunch of social networking sites, although not to YouTube.
-- thanks, Jim