It seems to me that less than perfect graduation rates…can be interpreted in a two ways. The first, as Leonhardt has suggested, is as a failure of educational institutes to provide their students with the resources necessary to graduate. An alternative interpretation, however, is that the numbers demonstrate that universities are casting a wide net for potential college graduates, and then letting students determine on their own once they get there whether they will sink or swim.
From a Rawlsian viewpoint, this offers a number of nice attributes for society: we are able to identify our college graduates later in the process than if we restricted admission only to those we knew were guaranteed to be able to graduate from college. Yes, some students will fail, but others will get a chance they might not have had with more restrictive admissions policy. Moreover, one can argue that for a college degree to have any meaning, at least some students will have to fail to achieve it; otherwise, the diploma simply equates admission, and not any accomplishment while at the university.
Free Exchange has a few more criticisms.
The Dish 