While it's possible to use DRM etc to protect your videos, it ends up being a bigger hassle for you and your paying customers. No matter how hard you try, there will always be a way for people to download the videos. The harder you try to prevent that, the more difficulties you will make for legitimate customers.
Need more real world examples? See DRM in the music and computer game industries.
The best policy is to offer your content at a low enough price and make it very convenient for the user, that way piracy is impractical. You can't eliminate privacy, but you make it a bigger hassle than being a legitimate customer.