As a couple of others have noted, there is no reason to posit a false dichotomy - that one must use either Kahn Academy (or similar) or a "live" teacher. Short lessons like Kahn does are useful to review concepts/unit operations where a student is rusty. My wife teaches physics, statistics, and calculus at a small high school and is an adjunct at a local community college, teaching the CC classes in the high school. The best bang for the buck for college credits around. Anyway, her biggest complaint is that too many of her students have been coddled in lower level classes and have either never mastered the pre-requisites or simply not retained them. Kahn's videos are one of many helpful resources for such students. The goal is to transform students into self-directed, life-long learners. This is really the only path to success, because the half-life to obsolescence of any technical course of study is so short.
Prof. Jean-Claude Bradly at Drexel discovered that students actually preferred pod/vodcasts of lectures (they could pause and watch on their schedule) and it freed up class time to work problems and answer questions. I see Kahn Academy videos in this same light. Are they perfect? No. can they be improved? Yes. Will polite, constructive criticism be better received than snarky comments? Absolutely! In this regard, the cliche "everything i needed to know, i learned in kindergarten" has some merit - things are a lot better when everybody is polite and plays nice in the sandbox.