See this post at Seth Godin's blog to see the curves in question...
A. Hero Curve (what everyone predicts they can achieve)
B. Loyalist Curve (several cash cow products with this curve create a saleable business)
C. Warrior Curve ("true-believers" and evangelists live on this line)
D. Hindsight Curve (only a co-dependent optimist can survive along this line)
I am surprised that Seth's latest book is riding on the Loyalist curve. Not that I'd like to make any effort to out-guess Seth, but has he considered the different methods on communication that would effect the sale of his book over the long haul?
As a blogger with a large audience it makes sense that the launch of his book would show an immediate spike in sales (a large audience of people electronically connected that knew the instant his book was available). I believe his book's tale will play out on a Hero curve simply because the rest of his audience will become aware through all of the older, slower methods of finding things out.
I wonder if there is one more curve that accounts for this disparity in the speed of knowing.