If I am informed correctly, the lecture format developed in the early days of the university because books were so damn expensive. As no student could afford them, the university would offer the option of gathering around a professor while he actually read aloud from his books. Back then, lectures made sense as means of learning. Lectures still make sense because (i) some lecturers are entertaining, (ii) lectures offer good opportunities to check out whether there are attractive members of your preferred sex around that you haven't talked to yet. As means of learning, they are terribly ineffective, as anyone knows who spent three days reading a book and was surprised to find that this provided as much useful information as all of a one-semester lecture.* The difference between then and now is that these days, books are cheap. (Yeah, I know what they charge for textbooks in the U.S. I also know what they charge for college in the U.S. The comparison makes books look really cheap.)
I hence always found strange the theory that has been prominent on the kinds of blogs that I read: that universities are on their way out because you can now get cheap or free lectures online. Eric Crampton, a professor of economics, describes this view, only to unsubscribe from it:
Whenever I read stories about the growth of MITx or other equivalents, I get a bit nervous about the long run for academics. I've consoled myself with that academia is really a rather more complicated product than just book-learning: there's all kinds of consumption and complex human capital formation bundled in with it; MITx can't easily replicate that bundle.
In order to make that argument, he more or less fully subscribes to Noah Smith's view of what it actually is that college provides. But you don't need a theory to come to the conclusion that MITx and the Khan Academy are no threat to universities. That's because universities have long been surviving the cheap availability of substitutes for lectures that also provide book-learning. They're called books.
*For the same reason, I hardly ever watch videos of lectures or presentations. I can take in the same number of words in a third or fourth of the time, and I'm not a particularly speedy reader.