Why is it so hard for NCAA athletes to transfer?

Warren Zola will have a column on this topic in the coming days, but in the meantime, the New York Times examines NCAA rules for colleges when players seek to be released from their scholarship and transfer schools.  Adam Himmelsbach interviews several people for the story, including yours truly, and it comes in the wake of Danny O'Brien and Todd O'Brien's difficulties in leaving one school to play for another.  Compare how student-athletes looking to transfer are treated with other students who seek transfer from one school to another for academic (or other) reasons.