Many companies ask you directly for feedback. Duke's Career Management Center also asks students for feedback and will pass the word around.
As for us not sharing the names, think of it this way:
As a b-school candidate, you are pretty anonymous. You are one of a gazillion candidates. The connection you have with a given school is relatively impersonal. If you knock school X and would never want to go there anyway, School Y will never know how you felt about X or probably much care. The likelihood of negative repercussions getting back to you is pretty slim.
On the other hand, the work world is much smaller and much more personal. At this stage in recruiting - Round 2 interviews and up - you lose that anonymity because there just aren't that many of you. In a given industry, word can get around. Witness Pelihu's posts about week on wall street events and how the alumni network was abuzz with who did what.
It's not that I don't trust this group of folks, but it's just too important to risk. And overall, there's just a certain level of professionalism around recruiting that requires an enormous amount of tact and discretion. I carry that to this board.