Why are there still human teachers? 
hackerblues: What advantages do you think software offers in this respect that books don't? All I can think of are:
a) Logging successes/failures
b) Suggesting questionsBoth of these are partially replicated in books by
a) Having a list of answers at the end of the book the student can check their answers against and so mark their own work.
b) Students can look at the entire list of exercises and choose whichever they think appropriate - the very height of a "personalized learning experience"Think about the reason we still have human teachers even though books have been available for hundreds of years and you'll probably answer your own question.