I gave birth at a medium-sized teaching hospital and everyone except housekeeping took a tour into my room that day--even a group of paramedics who had never seen a birth!
That being said, though, had I known any of them on a personal level I would have shouted them back out to next Tuesday. Just too odd.
As a student starting my OB rotation soon, I know of at least 2 friends who will deliver @ my hospital during my rotation. If I get assigned to either, I will pop in, say hello (as long as they are not in transition or pushing) and then ask for a different assignment.