Lacking Natural Simplicity

Mark Arsenault, president of Gold Rush Games, had some unhappy observations on the health of the RPG industry in his post Changes in the Air: A GRG Update for our Fans on the Gold Rush Games forums on May 5th. One item in particular was the small sales size:

[T]he general consensus is that sales are down across the board (with new product sales in the 200-800 unit range; very low compared to just 2 years ago)...

The market leaders, of course, are selling in larger quantities, but even if these sales figures are only common among the second tier companies it's still ominous. Why have sales declined like this? Ron Edwards has argued in the past that this is due to the myth that a successful game must be an large rulebook supported by an ongoing stream of extensive support materials. Others have suggested that part of the problem is the supplement treadmill.