With a precision that we can only assume they are winking at, Google has announced that there are 129,864,880 different books in the world.
The post, by Leonid Taycher, explains some of the decisions Google made when deciding what constitutes a book, but there are obviously cans of worms by the truckload waiting to be opened if someone really wanted to pin this number down. Or, put differently, there is no conceivable way of pinning this number down because books are too important and too ancient to be capable of anything except arbitrary definitions. Google does it in part by making one-at-a-time human decisions: "Twice every week we group all those records into 'tome' clusters, taking into account nearly all attributes of each record." It's dirty work, but someone has to do it.
Actually, it's dirty, messy work that would seem perfectly suited to an expert-amateur collaboration: Librarians and readers. For example, just think how valuable it would be to know that two books were almost considered to be the same! Not to mention all the other relations among books that we could together could discover and publish.