On-the-page breadcrumbs often mirror the directory path anyway. To my mind, it stands to reason that that clear, human-readable, hierarchical URLs can enhance a site's usability. But I have no idea if users actually look at them.
 Note: I understand that there are security issues with URLs that are better off not readable by humans in certain circumstances, and there are also database-query issues that I'm not very familiar with. I'm imagining a more straightforward scenario navigating over a series of largely static pages, e.g.
school.edu/admissions/apply-today/. Having produced that example from thin air, I just went over to Amazon (out of curiosity for a real e-commerce example), and its URLs aren't like this. For instance,
Books > Computers & Technology > Web Design gives me
http://www.amazon.com/s/ref=lp_5_nr_n_18?rh=n%3A283155%2Cn%3A%211000%2Cn%3A5%2Cn%3A3510&bbn=5&ie=UTF8&qid=1389965780&rnid=5. Perhaps this suggests the answer to my question is "No."