Long Tail definition

 

The phrase The Long Tail was first invented by Chris Anderson. The concept drew in part from an influential essay by Clay Shirky, “Power Laws, Weblogs and Inequality” that noted that a relative handful of weblogs have many links going into them but “the long tail” of millions of weblogs can have only a handful of links going into them.

Source: http://www.christosmargetis.com/2007/01/18/long-ta...

This is the best dissertation I've seen on the "long tail". The phrase has been used quite a bit in discussing Web 2.0 phenomena. This puts it in context.