NPD tends to get direct retail data, at least in the games industry. Would be interesting to see their raw reports to get a better feel for where their numbers come from. For games, their current growing blindspot is digital distribution.

Someone in the comments thread there said 29% of the US mobile market is prepaid, and 79% of those are now smartphones. No source though for his numbers, so who knows. Even with 79% of 29% likely being all Android, their overall numbers still don't make sense.