Of course, Khan went on to hire Hart, a partnership which could be yielding all kinds of fruit. If anybody has noticed Khan innovating on his format since he picked up Hart, drop me a line in the comments.
The KA lectures may or may not be effective in helping people with math, depending on your idea of â€œhelpingâ€. The KA problem sets are almost certainly going to give many students the impression that they know and understand something that they do not. Naive teachers may be taken for a walk along this primrose path as well. For that reason I think the problem sets could be quite destructive. I donâ€™t object to checking for mastery, but KA doesnâ€™t even come close to having assessments that measure mastery.