Part time team member

Mark Levison descibes from his heart how it is to be an agile developer, working at a distance. The conclusion is straight forward: don't do it.
We've experienced the same thing with part time team members, in other words students working with us part time. With the best intentions we wanted them to be "full" team members but that is not reasonable. Not being there don't give you the same chance to have that collective responsible for team objectives. You can take responsible for tasks when you're there, but not when you're not. I guess it would be different in a completely distributed team where everyone is facing the same problems derived from physical distance.