visiono, what methods are you talking about? Personally the only thing I can think of would be to add watermarks, but that doesn't really keep it from being stolen per-say.
Keeping right click actions from happening is the only other thing I can think of, but that honestly doesn't do much in the way of keeping people from stealing. But I really have no idea how you could stop the theft, the people stealing will almost always find a way around it. To me the only way to keep people from stealing it is to never upload it to the web in the first place.
For megasites, I am guessing they still gain enough revenue even with the theft, and that most people who are downloading the stolen content would have never paid for it anyway. That's just my
