A former Apple employee has created an app called iPhoneTracker that pulls data from your iPhone backups in iTunes and then displays pretty much everywhere you've been lately. There's a huge storm of privacy concern going on as a result.
You can certainly tell what cities someone has been to, but most of the location data is way off. Hundreds of miles off in my case. I can't imagine anyone finding much use in this as local data is grossly unreliable.
Here's my map. Larger dots are correct. I have been to Birmingham and Jacksonville, but the smaller dots in places like Northwestern Alabama and the central panhandle of Florida are completely incorrect.