"I bet we'll see the problems for another two to four weeks," Munster said in an interview with ComputerWorld. "Early demand has been more than they expected [because] they knocked it out of the park on the first weekend."
With its high-speed 3G capabilities, integrated GPS, and lower price, the iPhone 3G was a highly anticipated device. Despite activation issues and long lines, Apple sold one million handsets over the launch weekend.
But this initial sales success also has depleted stock, and an earlier report this week based on the iPhone availability widget determined that the smartphone was sold in more than 21 states.
Munster said one reason for the short supply is the international availability of the new iPhone. Last year, the iPhone debuted only in the U.S. market, but the iPhone 3G was rolled out in 21 countries last Friday.
International demand for the iPhone 3G has been high, with a preorder rush bringing down a U.K. carrier's Web site.
"Sales internationally have taken inventory away from the United States," Munster said.
AT&T's 1,200 retail stores also are nearly out of iPhones, a representative for the carrier said. The wireless carrier's stores do allow customers to buy the new touch screen smartphone in advance, and return to the store for activation once it comes in.