The WCC is actually a fairly new addition to medical education. Schools started doing it in the 90's. Read about it at every medical student's favorite resource:
http://en.wikipedia.org/wiki/White_coat_ceremony
Schools do vary, however, in when they hold their WCC. I heard somebody on SDN say that they had one in April.
I am one of the critics of it because I think that white coats create barriers. With the progressive nature of medicine, I would have thought that ceremonies like this would be fading out rather than gaining in popularity. I know of no schools that don't have a WCC, but I suspect that Mayo's dress code (which doesn't include white coats AFAIK) miight suggest that they don't have a WCC.
I think that I might be more accepting of the WCC if it were placed after step 1 when we've actually completed the "pre-medical" stage of our careers. And yes, I do believe that M1-2 is still considered pre-medical because the content is what most lay people think you're learning in college as a pre-med. It's kind of a joke for me to walk around behind a doctor for a couple of hours with a white coat on when I'm not even allowed to do any procedures. I don't exactly feel like a "student doctor" as an M1.