Sprint Nextel dropped the most in more than a month after Sanford C. Bernstein downgraded the company to underperform amid concern it won’t sell enough iPhones to afford its ‘punishing’ commitment with Apple, notes “Bloomberg” (http://www.bloomberg.com).

The high costs of network upgrades, a “stupendous debt burden” and a “hobbled 4G offering” that may be insufficient to sell millions of iPhones this year, are some of the challenges faced by the nation’s third-largest wireless operator, analyst Craig Moffett wrote in a research note to clients. He had previously rated the shares market perform.