Make sure you are using a mobile device running iOS 4 or later. If you receive an "Opt out not successful" message, please wait a few hours and try again.
A few things you should know:
You may still see the same number of ads as before, but they may be less relevant because they will not be based on your interests.
You may still see ads related to the content in an application or based on other non-personal information.
If you use more than one Apple mobile device running iOS 4, you will have to opt out from each device individually.
Opting out applies only to Apple advertising services and does not affect interest-based advertising from other advertising networks.
To be clear, you can't avoid the ads
You just opt out of the personalization of ads, similar to Google's http://www.google.com/ads/preferences/