Gray-market use of the iPhone is extremely widespread, according to cellphone advertiser AdMob. The company collects statistics on the devices and locations associated with ad requests and impressions, normally for the purposes of targeting its marketing; in a recent study however it observed that while only 25 percent of worldwide AdMob requests are from smartphones, the iPhone has moved into the top 20 devices. Most requests are served to two countries with official iPhone support -- Germany and the US -- but many requests are being directed to nations where Apple has no official iPhone presence, such as Canada, Mexico, Brazil and the Netherlands. The Chinese city of Hong Kong also ranks unusually high in terms of iPhone advertising.

In most such cases friends or third-party companies are exporting the phones, as Apple does not allow the sale of the device outside official regions. The company is attempting to combat this lost carrier revenue, though, and has already forged deals with telcos in places across Europe, Asia and Africa. Notable exceptions include China and Russia, home to the largest number of gray-market iPhones.