I'd say on the list, around 20% had a listed a school that was not a USNews top 30 undergrad
Sample of people on "Wharton 2010" facebook group (U.S. schools only) - first three pages displayed (alphabetically): Harvard, Univ. of Chicago, Cornell, Princeton, UVA, Emory, UNC, Univ. of Pennsylvania, Harvard, Berkeley, Princeton, Dartmouth, Brown, Harvard, Brown, Princeton, Carnegie Mellon, Caltech, Univ. of Illinois, UT-Austin, Amherst, Duke, Yale, Williams, Princeton, George Washington Univ., Harvard, Harvard, Univ. of Pennsylvania
I am not trying to make a point...In fact, I wish the class was more diverse in terms of school backgrounds! It would be nice to see as much diversity as possible!