By owning one small, niche category with good timing and an easy push, if it drives enough sales, you can basically trade up in your other categories. If you get the right combination and self-sustaining beyond your local allies, you could get traction across the board and build a legitimate best seller in an ever widening space which just furthers the cycle. It's the same as Hacker News.

And it reminds me of another book I read last year.. ;)