I assume that you’ve heard at least some of the wailing and gnashing of teeth about iDevices caching location information, allowing for the use of an iPhone or the computer that it syncs to as a record of the owner’s physical movement.
Well, if you would like to see how thorough it is, check out iPhoneTracker. This is a simple application for OS X that will search the hard drive of your computer, find the cached information from an iDevice that’s synced to that computer, and build a map of where you’ve been with it. Ta-da! If you’re using a Windows machine, check out the Linux port iPhoneMap under Cygwin instead.