Some programs such as Google Maps offer services that use your computer's location information, but Apple's privacy change was made primarily for iOS devices including iPhones, iPad and iPods. These devices offer a slew of applications that want to use your location data for everything from Foursquare check-ins to geotagging photos. Although Apple's policy change was recent, iPhone applications have been able to access your iPhone's precise location information since iPhone OS 3.
Under the recently released iOS 4, Apple has added new controls for location services that help you understand how your location data is being used. As was the case with iPhone OS 3, whenever an iPhone application wants to use your location data you must explicitly authorise it do so. In iOS 4, after that first-time authorisation, a small arrow appears on the top right of your iPhone screen every time your location information is being accessed by an application.
Apple also gives you granular control over which apps can use your location data in a new panel under Settings>General>Location Services. From here you can turn off all location services for your iPhone just as you could with iPhone OS 3. New in iOS 4, however, is a list of apps that are able to use your location data. You can choose to permanently block any app using your location data including Apple's own applications like the camera and Safari.
The location settings control panel also places an alert icon next to any application that has accessed your location in the last 24 hours. In my tests, once you've blocked an app from accessing your location in the control panel, the blocked app will not ask you again to access your location data. So if you want to turn location access back on you will have to do it through the settings panel.
Overall, Apple appears to be doing a pretty good job with your location data, however there have been some criticisms over the new policy. Apple does not specify, for example, whether or not it will still track your location even with the Location Services global control turned off. It's also not clear how long Apple intends to store your location data, and what kind of safeguards it has in place to protect its database of location information. I've asked Apple for clarification on these points, and will update this post once I hear back from the company.
Cell phone location data is shaping up to become the next major privacy battlefield for civil rights advocates. NPR's On The Media recently reported that requests by the police for cell phone location data have become routine.