Cardistry is juggling. There's no secrets to protect there, so as long as someone isn't teaching someone's copyrighted material (ie: something that's been put into a product for purchase) there's nothing wrong with it.
With cardistry, what you see is what you get and what you have to learn. Many people learn cardistry moves JUST by slowing down performances even. Teaching cardistry on You Tube is usually not a problem.
However, it becomes a problem if the move is being sold. Teaching a move up for sales is definitely not ethical at all, but the cardistry community creates way less ruckus about it than the magic community. At times, even creators of a move that was up for sale at some point (or even is, currently), teach it on You Tube or give others permission to teach it on You Tube, for free. Of course, that's their call and only they have the right to decide if they want to do that.
The secrets of cardistry lie in the grips, the small tips and tricks, the way you incorporate more than just your fingertips into the art form. These are also the reason why some people do a move and look kind of cool, while there are others who make that move look simply beautiful. And that is why we should learn directly from creators and the sources they post/upload/sell.
What more, there is so MUCH of cardistry all around, that I don't even see the point in trying to look for free tutorials of otherwise paid moves. I could spend years trying to just SKIM through all the tutorials for all the moves already up on You Tube for free.
I agree with the previous comments. Magic on youtube is frowned on because:
(1) it exposes secrets, which is the point of magic;
(2) it gives away for free something that is often a commercial project owned and sold by a creator;
(3) it typically tends to be mediocre in quality.
Cardistry is a whole different phenomenon, and most of those three points don't apply to youtube videos teaching cardistry. In fact, the majority of good cardistry tutorials are freely available on youtube, like the ones here: