I agree that there should be at least a one year residency requirement.  Physical presence provides an opportunity for professors in doctoral programs to work face to face with students.  I believe this interaction is important to student learning and for the doctoral progam to be able to adequately assess student functioning and provide feedback.  Also, it allows for students to learn by first hand observation that which is modeled by mentors.  A residency requirement promotes student interaction that not only provides support but also promotes learning through shared information. Given that most communication between individuals is nonverbal, physical presence seems important.