Apple is also allowing iPhone users to opt out of receiving Apple-based ads that are highly relevant to "your interests". You can opt out of the iAd experience by going to this link. However, opting out will only prevent you from receiving ads based on your interests. The number of ads you will see on the phone will remain the same. You might still receive ads based on a web site you are visiting or based on non-personal information. Also, opting out of relevant ads will cover only those that come from Apple and will not affect mobile ads you might receive from other networks. Just remember though that the more ads you see, the less money is coming out of your pocket.
Apple iPhone 4 Specifications