Regarding the post just below: Carr refers to Wikipedia as “a single source of information” — but is it? It’s a single conduit of information, but a conduit is not a source. What are the sources of information that emerge through the Wikipedia conduit, having undergone the Wikipedia filters? Well, there’s a great deal of dispute about that. Aaron Swartz — who not incidentally is instrumental in the creation of a more-or-less alternative to Google Books — wrote a fascinating and much-debated essay on this topic a couple of years ago. Check it out.