You are right. I've come to realize that the reason the site has garnered the attention it has thus far is mainly due to the comparison to Khan Academy. Otherwise, such services already exist (although one could argue that their execution leaves something to be desired).
The only reason I used Khan Academy in the slogan was to get the idea closer to mind (and to do it with as few words as possible). But the effect has been far more powerful than anticipated.
I'm really wondering now if I should remove any allusion to Khan Academy from the page. What do you think?