The answer to this question is depending a lot on who is the person answering. In my opinion everybody can learn something or a lot from any media. It depends a lot on how you are WILLING to understand and DOING it regularely to get an even better understanding.
The video/dvd/books can be a great training partner for those people that do not care to be in large crowds or just don't have the possible facilities nearby or at irregular times or no friends that would like to share their time on a regular base. A great advantage: YOU are in charge of when and how. If you did not see something you were wondering about how it would be done better ... just hit the rewind button and see it in slow-motion and as many times as you choose best. Of course most people will have to develop discipline for such training. What difference in learning is there compared to lessons not at your home?? You watch, you try to learn, but somebody is standing in front of you or you cannot pick up the pace etc etc. I am not trying to say that yoga  or training at a gym is not fun. On the contrary! It is fun, but it's nice to know upfront if you would like that new hobby of yours or just to get those loose ends questions better answered or you do not have to miss practice when the gymhours did not suit you due to extra hours at work etc etc. Most important is having fun without any injuries! Of course it would be recommended to try out your hobby in a place where they practice it and ask them all those question you have not gotten from that DVD/video ... maybe some feedback to chack up if you have been doing it right.
Discipline is not enough... you will have to stay busy and better your performance too. This means to check here and there if you could better that move even better. You will notice that while you improve you start seeing things differently, because after a while you'll not be a beginner anymore.Why can't you teach yourself? You are human, ain't you? Teachers are human, so that means we can teach ourselves too. It's just that you have to learn first HOW to LEARN and TEACH YOURSELF. Some will have more problems than others and have there the chance to get to know themselves/ better themselves this way. Do not give up on your first try... it might take you some time to learn some new thing or even learn something new in something you already thought you would know. Just keep an open mind and stay hungry to better all that you you and someday you will stand in front of a mirror and thank yourself for being the closest friend you have around. Selfknowledge would be nice too before we die, so why not start today and give it a try ;D. Start that new hobby. You can even sit on your stationary bike/crosstrainer etc. while watching another form of fitness training as long as you enjoy what you see and learn from it what YOU need. It's also used for inspiring yourself to keep on doing what you like to do even on those days you feel a bit lazy ;D.