Researchers have discovered that the iPhone is keeping track of where you go and storing that information in a file that is stored – unencrypted and unprotected – onto any machine with which you synchronize your phone.

…While it is not unusual for cellphones to track users’ location, that information is typically kept behind a firewall and it requires a court order for others to be able to access it. This isn’t the case with this particular file, raising serious questions about privacy and security.

Your iPhone Is Tracking Your Every Move (ReadWriteWeb)