The Long Tail theory suggests that our culture and economy is increasingly shifting away from a focus on a relatively small percentage of "hits" (mainstream shotgun approach for most products and markets) at the head of the demand curve and toward a huge number of niches in the tail.
Why the shift? As the costs of production and distribution continues to fall – new technology, Internet, etc. – there is now less need to lump products and consumers into "one-size-fits-all" bundles.
In an era without the physical constraints of shelf space and other distribution bottlenecks, niche goods and services are becoming economically attractive. Chris Anderson, editor-in-chief of Wired Magazine, wrote The Long Tail. It first appeared in Wired in October 2004.
The link above will take you to Chris Anderson’s Squidoo lens where you can access additional information.