The Long Tail
Coined by Chris Anderson, editor of Wired Magazine, The Long Tail was first an article, is now a blog and is on the way to becoming a book. Behind The Long Tail is the idea that there is tremendous value (and money to be made) in niche markets and products that are nowhere near the peak of popularity, but are now being discovered due to the prevalence of online recommendations and lists. In other words, one thing becomes popular (a book, song, etc.) and based on the fact that it may interest you, you also may be interested in other lesser knows works that are similar in some way. The new ease with which those lesser known works can now be recommended has opened them up to a whole new audience that otherwise would have never known they were there.
Beyond that specific application of The Long Tail principle, Anderson’s blog has begun exploring other areas where this concept applies. I find particularly interesting this post about why The Long Tail principle may work against Apple’s iPod Shuffle.
I highly recommend reading the original article and keeping-up with how this theory develops.