The company has huge debts coming due staring next year, for one thing. For another, it's committed to buying a whole lot of iPhones from . And for yet another, there's the dread prospect of the LTE iPhone 5, according to Moffett, that "poses new and lager risks" for the carrier.

"We believe an LTE iPhone will likely be badly disadvantaged on Sprint's network, potentially impairing sales ... at a time when Sprint is subject to a punishing take-or-pay deal with Apple," Moffett writes. "The problem is 4G. Sprint doesn't have enough free-and-clear spectrum on which to launch a competitive LTE network, and it doesn't have the money to clear spectrum that's already in use. We expect Sprint's competitiveness to begin to backslide when LTE becomes the nation's de facto standard."

And the iOSsphere is all over it. Surojit Chatterjee, , breezily announces that "2012 is going to be the year of quad-core-powered, 4G LTE-enabled ," that "4G LTE on the next iPhone is almost a 'done deal,'" and since Sprint hasn't released a 4G smartphone, "the launch of the new iPhone is expected to kill Sprint, as users will lean towards Verizon or AT&T for purchasing the upcoming iPhone."

Chatterjee, we suspect, kind of skimmed Moffett's analysis, because here's his take: "According to the $15.5 million contract signed between Sprint and Apple, the former has to buy minimum 25 million iPhones from Apple in the next four years. If Sprint fails to upgrade its network to LTE at a nationwide level, then these iPhones will go unsold and could cause Sprint to incur huge debts."

Sprint already has such huge debts that another $15 million looks like a drop in the bucket. And the new 's LTE chipset comes with advanced support for the highest 3G (or non-LTE 4G, depending on your choice of definitions) speeds available, which mobile carriers are still deploying. LTE subscriber growth in the U.S. has been spectacular in terms of the rate of growth, but at the end of 2011, the total number was still a fraction of all mobile phone users: 5.6 million, most of them on Verizon , according to . And it's also a fraction of the number of potential subscribers: Verizon claims its LTE network covers more than 200 million people.