In the book The Long Tail, ChrisAnderson? popularized the phrase, long tail, to describe the frequently occuring PowerLaw distribution in domains of social popularity. In these domains, there are typically a relatively (very) few number of "hits" that are very popular (the head), and a very large number of relatively (very) unpopular "niches" (the long tail). Anderson suggests that our culture and economy are shifting away from focus on hits towards focus on the long tail.
The reason why it is called the "long tail" is that social popularity graphs tend to follow ZipfsLaw. The hits form a sharp vertical spike at the beginning, and the niches form a long tail afterwards.
This shift is seen in a large number of places. Most relevant to the context here is the shift away from TheAuthor as revered genius towards a democratic or popularist or consumerist focus on TheAudience. Hence, a shift from TheBook? to OnlineCommunities.
Other interesting predictions is that the aggregate value of the LongTail of NicheMarket?s could be equal or at least significantly comparable to the value of the hits. While traditional retail is limited by the scarcity of expensive shelf space to stock products, digital retail has theoretically "infinite shelf space" (cf. EnlargeSpace), or at least a very very large amount of space which is limited by the AttentionEconomy?. For example, Amazon.com can stock and present millions of book titles to the customer, whereas a traditional bookstore would only be able to stock a few thousand (or a couple hundred thousand in the case of the superstores).
Of course, in the case of the online book industry, usually books are printed and stored in a warehouse until they are bought. This puts a finite limit on the number of titles available, even if the total capacity of the publishers' and distributors' warehouses are much larger than a retail bookstore. An alternate solution is to not produce an item until it is requested. Therefore, another prediction is that MassCustomization? in the 21st century will increasingly take over from MassProduction? (post-WWII). So, in that case, books will be printed on demand. Or CafePress? t-shirts are printed on demand.