According to Michael Mace, mobile developers across the board are reporting a decline in sales. Mace's key points are that there are not enough new smartphone buyers (i.e. most new smartphone sales are for replacement devices), the application sales are not tracking the growth of all smartphone platforms, and that smartphone users are less likely to need third-party software. While I'm not sure if I agree with that last point, Mace's article is well worth a read. Article