From Apple Support Page:
About iOS 6.1 Software Update
This update contains improvements and bug fixes, including:
- New button to reset the Advertising Identifier
To Reset Advertising Identifier, go to:
- Settings > General > About
- Scroll to the bottom of the page and tap on “Advertising”
- Tap on the “Reset Advertising Identifier” button
About Ad Tracking
Ad Tracking
iOS 6 introduces the advertising Identifier, a non-permanent, non-personal, device identifier, that apps will give you more control over advertisers’ ability to use tracking methods. you can reset a device’s Advertising Identifier at any time. And if you choose to limit ad tracking, apps are not permitted to use the Advertising Identifier to serve you targeted ads. In the future all apps will be required to use the Advertising Identifier. However, until then you may still receive targeted ads.