Why would you use a fake webcam?  Well, aside from the obvious voyeuristic uses, having a bit of software between your home webcam and the Flash-based video world might just prevent an unauthorized webcam snapshot.  Because it makes the system more complex to the attacker who would assume either a single webcam or a webcam that can be turned on and off via Flash.  Which is not true of a webcam exposed through the mixing layer of CamCamX.