What use are lectures now that everything can be found online?

I have often wondered what students were actually learning when they were sitting in large classes listening to my lectures. I had also read that standard lectures are not an effective way for students to learn Gibbs . So in 1997 I decided to try to find out:

• why my students attended lectures
• how useful they found lectures
• what they learned from the lectures

There is virtually no information on these questions in the literature that is specific to mathematics.