Taxmom shines the life-giving glow of her wisdom on MOOCs:
… I think the problem with online education is that learning a discpline is, by defnition, hard (hence "discipline"), and 98% of the people need someone to lead them through it. How many times have we all decided to learn something new, skimmed the surface with ease, and then about 2% of the way in realized that there is something pretty basic that is either a) really hard to comprehend or b) requires skill and practice, and building up stamina, or both.
With guitar, everything is rosy until you have to play an F-chord.I'd add:sociality. People still learn more from each other than they do from the teacher. Or even if not directly from each other, then from the buzz of learning in the vicinity.
With algebra, everything's peachy until you have to do that (a + b) (a - b) thing.
With a language, everything is great until you realize you have to keep more than 8 words in your brain at one time, and that words don't necessarily look the same in the dictionary as they do on the page.