Over the years I've found lectures less and less useful to attend in person as profs and other presenters post their lectures and powerpoint slides online. I can just watch/read those and get everything I need from those materials, then when I'm in class I can ask much more useful questions and cover the details that really make the difference.

I love how the Khan Academy is institutionalizing that idea. I can't see any reason that lectures need to be done in person, but being able to work through sticking points with someone. Now that is valuable.

I really do think Sal Khan will revolutionize teaching. At least in the areas this model is applicable.