What Do You Think of Youtube as a Learning Tool?

In regards to learning, the downside of youtube is that students try to play things that are not appropriate for their learning level.  I had one student who goofed around with one youtube example and never learned to play the whole song, and I feel he missed lots of the fundamentals which would have taken him further in the long run.  A comparison is someone trying to get medical advice from the internet.  While a certain amount may be helpful, there is no substitute for finding a "sensei" and being a disciple.  I do have a youtube channel where I demo proficiency skills that are are part of a learning sequence.  The skills are part of my "Guitar Essentials" which I use in my High School Classroom.