From Nielsen are some interesting stats regarding mobile app usage and popularity, based on the app download habits of 4,200 people based in the US. Turns out games are the most used category of smartphone apps for last May 2010 (no surprise, actually), with news/weather and maps/navigation/search a relatively far second and third respectively.
On practically all smartphone platforms, Zuckerberg's baby is a clear winner. For iOS, Blackberry OS, and "other" devices, the corresponding Facebook app is a clear leader in terms of usage. The odd platform out was the Android OS, with its users using Google Maps more.
Last but not least is the average number of apps installed by platform. Apple's mobile OS is a clear winner at 37, with Blackberry bringing up the rear at 10. Windows Mobile slightly fares "better" at 13, followed by "Palm" with 14. Android comes second at 22.
How does your own mobile app usage correspond to Nielsen's averages? Let us know through the comments below.