It's not the first time privacy issues arise from mobile devices. Today at the Where 2.0 conference, there was a talk on the discovery that your iPhone, and your 3G iPad, is regularly recording the position of your device into a hidden file.
From the O'Reilly Radar: "Ever since iOS 4 arrived, your device has been storing a long list of locations and time stamps. We're not sure why Apple is gathering this data, but it's clearly intentional, as the database is being restored across backups, and even device migrations. [...] What makes this issue worse is that the file is unencrypted and unprotected, and it's on any machine you've synched with your iOS device. It can also be easily accessed on the device itself if it falls into the wrong hands. Anybody with access to this file knows where you've been over the last year, since iOS 4 was released. [...]
We have built an application that helps you look at your own data. It's available at petewarden.github.com/iPhoneTracker along with the source code and deeper technical information. [...] An immediate step you can take is to encrypt your backups through iTunes (click on your device within iTunes and then check "Encrypt iPhone Backup" under the "Options" area)."
This topic was also discussed over Slashdot today.