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On your iPhone, you can go to: Choose Settings > Privacy > Advertising.
If you've turned on Limit Ad Tracking, you can restore interest-based ads by turning Limit Ad Tracking off.
Note: You must be logged in to iTunes for these settings to apply to your account. We also recommend that you restart iTunes Radio for the Limit Ad Tracking setting changes to take effect.
By opting out:
You may see the same number of ads as before; however, they may be less relevant because they won't be based on your interests.
You may see ads related to the content in an application or based on other non-personal information.