Apple has recently launched their location aware iAd mobile advertising network that targets devices running on the iOS 4 software platform. These devices are the iPhone, the iPod and the iPad.
However, you can easily opt out of these geolocation ads.
• Open Safari on your iPhone, iPod Touch or iPad
• Visit http://oo.apple.com/
• and you're done.
(Keep in mind that you may still receive ads but they won't be 'location aware' of you)