According to this San Francisco Gate Article, many Apple stores and AT&T retail outlets are still having problems keeping the 3G iPhone in stock, more than a month after the initial launch of the device. High demand, availability in 22 countries, as well as the fact that the 3G iPhone can’t be purchased online were factors leading to the shortage of units. It has been estimated that over 2.5 million 3 G iPhones will be sold by year’s end. The shortage may finally ease once the iPhone 3G devices begin selling in Best Buy stores in September.