A Wall Street Journal investigation examined many popular iPhone and Android apps to determine what personal information is collected by each app and to which third parties it is sent:
An examination of 101 popular smartphone “apps”—games and other software applications for iPhone and Android phones—showed that 56 transmitted the phone’s unique device ID to other companies without users’ awareness or consent. Forty-seven apps transmitted the phone’s location in some way. Five sent age, gender and other personal details to outsiders.
The findings reveal the intrusive effort by online-tracking companies to gather personal data about people in order to flesh out detailed dossiers on them.
This part is also interesting, but probably not surprising given Android’s open-source nature:
Among the apps tested, the iPhone apps transmitted more data than the apps on phones using Google, Inc.’s Android operating system.
The complete results available in an online database.