Estimates from industry analysts of the resulting number of defections to Verizon from AT&T range from one million to six million. John Hodulik, an analyst at UBS Securities comes in somewhere in the middle. He predicts that AT&T will sell 8.8 million iPhones in 2011, down from 15.6 million in 2010.
Of the 13.3 million Hodulik expects Verizon to sell in 2011, about 2.3 million will be to AT&T refugees, he predicts. An additional 10 million will be current Verizon subscribers who upgrade from other devices, and the rest will come from other carriers.
If six million of its customers defect, the $6 billion in lost annual revenue would amount to about 10 percent of AT&T's wireless sales in 2011 and 4.8 percent of total revenues of $126 billion in 2011, according to UBS projections.
On the other hand, while AT&T has reason to worry about losing the lucrative iPhone arrangement it has enjoyed since Apple introduced the device in 2007, the damage may not be as severe as many anticipate, for a number of reasons, mostly related to financial barriers to switching.
Despite the well-reported call dropping and other service issues in some cities and neighborhoods, many iPhone users do not report unusual levels of call dropping beyond what might be expected from any carrier, at some times, and therefore presumably do not have overwhelming incentives to change carriers. Churn possibly will be highest in New York and San Francisco, for example.
There are financial barriers as well. Contract termination fees, though pro-rated, could run up to $325 for a consumer at the start of a new contract. About 15 million of 23 million iPhone customers appear to be on such contracts.
Devices used on Verizon's network will not multitask, supporting both a phone conversation and Web usage, for example. For many customers, the cost of service on the Verizon network might be more than they have been used to, on the AT&T network.
AT&T says its 3G network is faster than Verizon's 3G network, and one does not hear Verizon disputing that in public.
Perhaps most significantly, many iPhone users are on family plans. Switching every user on a plan because one or two iPhone users want to migrate could pose barriers as well. Also, many users might want to switch, but then discover that Verizon Wireless prices are higher than AT&T's, in many cases. Whether that makes a difference is tough to determine at the moment.