Computers are helpful, but the stacks cultivate intuitive bookish instincts. Those instincts may not be quantifiable, but they produce discoveries that the rational structure of electronic databases almost inevitably preclude. It's like in Star Wars when the ghost of Obi-Wan Kenobi tells Luke Skywalker to turn off his computerized targeting system and "use the Force" instead.
And I have to wonder how "Professor Benton" thinks the stacks got organized in the first place -- perhaps by the (presumably intuitive) library fairies? What makes the LoC catalogers (or, in the case of old Widener holdings, Harvard catalogers) better at making serendipitous connections than Google's algorithms, which I've also known to produce fascinating juxtapositions for various searches? This sort of sentimental rubbish makes me turn more and more to Clay Shirky's "Ontology is Overrated," about the kind of multiple-user-generated information that can be used to organize digital information in interesting and useful -- yes, even serendipitious -- ways.