My old biomechanics professor, Benno M. Nigg at the University of Calgary, says … not necessarily:
His overall conclusion: Shoe inserts or orthotics may be helpful as a short-term solution, preventing injuries in some athletes. But it is not clear how to make inserts that work. The idea that they are supposed to correct mechanical-alignment problems does not hold up. …
NY Times – Close Look at Orthotics Raises a Welter of Doubts
He’s about to release a new book titled Biomechanics of Sport Shoes.
Of course many people swear by them, including this guy.
Gymnastics Coaching.com 