I created instructional videos that should only be streamed (viewable while logged in). There is currently no way to prevent downloading (I sent a tech request and received a reply confirming this fact). Some of the course video content is unique and required a lot of development time. If downloaded there is the potential to distribute without permission.
I'm using Screencast-O-Matic pro to create the videos, but they are .mp4 video files uploaded through the files menu and linked in modules.