In my opinion, however, there are certain things about tango that we can learn from Youtube and things that we cannot. I am speaking from my own experience in using Youtube as a learning resource as well as input from top teachers in Buenos Aires (those on the local and international performing circuit).
So what can we learn from video? Well, one thing that I think is very good to learn from video is musicality. If you watch the famous dancers perform you will see how musicality is used - how dancers use rythmn, pausing and pace to create beauty and tension in the dance. A teacher famous for his musicality is Fabian Peralta. It is really valuable, especially for leaders, to see how dancers such as Fabian use the intricate rythmns and melodies of traditional tango music to create the dance.
Another benefit of video is to observe dancers' general "style", that is , their posture, embrace, fluidity versus rigidity in their movement. For women, you can see, for example, how the tanguera uses her feet to create elegance and adornments.
Finally, we can learn about the footwork of the lead and the followers' response. But here is where my opinion of video as a learning tool goes down the drain. In tango terms, the explication of what produces the lead ie. sublte changes in the embrace, changes in the forces between the bodies, rotations, types of linear and centrifugal energy forces, balance and axis are not observable in video. Likewise, the follower can see where she should put her foot but she can't see what she should be doing with her core muscles, her connection to the floor and to the partner, the types of resistance she should offer and how she can achieve optimum balance.
Even well known Youtube material such as ""Dario's Tango Guide" gives only rudimentary information about the lead and follow. Make no mistake, I like Dario and his guide, and its stucture is useful for people living in remote areas. But once again, if anyone is trying to learn tango by figuring out what to do with their feet and legs, they have got only half of the story. The result is dancers who try to do complicated moves without the fundamentals of the dance.
I do prefer prefer online teaching summaries from Oscar Casas and Homer Ladas. They provide a window into complex and fascinating technique of tango. But what they dont give you is feedback on how you are doing. There are many dancers who have learned steps from Youtube and nobody has explained to them how they can improve to make it more pleasant for them and their partner.
SO.... you've already guessed what the conclusion of this article is...... I don't believe that is possible to learn good tango from most of the material out there on Youtube. Better video resources where teachers give much more information are available for purchase but beware of those that teach you "the steps". Finally, tango lessons from experienced teachers who understand and can communicate the complexities of tango are worthwhile! Take them, challenge yourself, enjoy the subleties and make yourself the best tango dancer you can be!