If you just have the products at the Head, you find that very quickly your customers want more and you can't offer it. If you just have products at the Tail, you find that customers have no idea where to start. They're unable to get traction in the marketplace because everything you're offering them is unfamiliar to them...And you, dear reader, may be thinking - yes yes, I get it: bookstores have "products at the Head" and libraries have "products at the Tail". Ah, but then consider this aside:
A good example of why this is so necessary is the story of MP3.com, one of the early online music services... It let anyone upload music files that would be available to all. The idea was that the service would bypass the record labels allowing artists to connect directly to listeners... But although MP3.com grew quickly and soon had hundreds and thousands of tracks, struggling bands did not, as a rule, find big new audiences and independent music was not transformed...I consider this evidence why we need a social library catalogue.
...(As an aside, it's worth wondering why MySpace, which has a free independent music model that is very reminiscent of MP3.com, is such a success. The answer at this point appears that it is a very effective combination of community and content. The strong social ties between the tens of millions of fans there help guide them to obscure music that they wouldn't otherwise find, while the content gives them a reason to keep visiting.
On that note, if you have any readings or research you would like to recommend on the social nature of academic research, please let me know.