Credibility: What employer understands the value of Udemy or Coursera courses? Essentially none. And understandably so.
Structured curriculum: No high school student today will spend on their own time, instead of going to university, 1-4 intense years of Udemy or Coursera courses. A very large majority of high school students haven't the slightest clue what they want to spend their life doing. Without any clue, there is no way they will have sufficient drive on their own to lead their own education efforts.
I haven't seen anything from either of these websites that even come remotely close to solving these issues.
Whoever solves these problems first stands to reap the biggest rewards.
if your not getting credit, what does the name brand mean?
some people may get a kick out of taking a 'Stanford' class (myself included, I took the original AI class)
those people will get discouraged quick if they go through the whole class and don't have a good outlet for that knowledge
I see two potential outlets, 1 something to put on your resume that will get you a job,
or 2, specific knowledge that will let you complete cool, even marketable project independent of a resume line
1 is a tricky proposition for these classes, until if figures that out, whoever figures 2 out will be the winner
I went all the way through the AI class, even got over 90%, I felt like I understood a decent amount of theory, still a ways from actually being able to go out and complete a project on my own