According to MacRumors-
“Some further digging into the newly released iOS 4.3 developer build has revealed settings for a new feature called “Find My Friends”. The strings are associated with the Settings app and is related to “MobileMe”. The obvious interpretation is that Apple may be looking to offer a location-based friend-finding service like Loopt and Google Latitude.
Services like Loopt allow you to find your friends who near you at any given time by leveraging your mobile phone’s GPS signal. The constant updates can broadcast your location to your friends to know who is nearby. Obviously, these sort of systems are opt-in only, but shows what Apple maybe up to in fleshing out their MobileMe service.”
Stay tuned for further updates on iOS 4.3!