Yesterday, an app was released that was able to read a file generated by iOS (and backed up to computer with iTunes), that shows where your iPhone or 3G enabled iPad has been since the day you purchased it. The file is called consolidated.db and uses cell tower information to give a guide as to where you have been.
Although there’s some obvious privacy questions here, the main questions are why this is allowed to happen, and what exactly does it track? A map of what the consolidated.db file looks like when placed on a map… program available here.