If you don’t want iAd to utilize data tracking cookies and location tracking to serve up relevant ads based on the info, you can opt-out to the service and feel just a less bit spied upon.
1. Go to your iOS4 iPhone or iPod Touch.
2. Open the Safari browser.
3. Go to http://oo.apple.com .
4. You should come to a page that states that you have successfully opted-out.
If you have multiple iOS4 devices, you will need to do the above for each device.