Self-ed has a harder time obtaining legitimacy, in part, because nobody holds you accountable to that.
My theory for why it's Udacity/Coursera/edX that's getting people taking online education seriously, in a way that OCW/Pirate Bay/videolectures.net didn't, is: hardly anyone actually used OCW/Pirate Bay/videolectures.net, 'cause social pressure + project/exam deadlines are a necessary motivator for practically everyone.
(Additionally, there's this meme that learning stuff should be fun. So maybe if people who self-study aren't having fun, they assume they're doing it wrong, and quit. But school forces you past that with its project/exam deadlines, etc.)
(Not to say that learning stuff can never be fun, but it's not really in the same league as Facebook and video games for most folks.)
BTW, didn't Scott have some kind of undergrad degree before this project?
Followup to: MIT Challenge: blogger to attempt CS curriculum on own
A year after he announced it, productivity blogger Scott Young has successfully completed his "MIT Challenge", an attempt to work through that institution's undergraduate computer science curriculum independently, using the large selection of online material that it has made available.
His three pieces of advice for independent learners are worth noting: