Andrew Jay Schwartzman, the senior vice president and policy director for the Media Access Project, aired similar concerns and said that the proposed deal would run into roadblocks from government regulators.

"If approved, this deal would further increase costs and decrease choices for the public," he said. "The FCC's National Broadband Plan, issued last year, warned about the absence of sufficient competition in the wireless market. The possibility that three players would control nearly three-quarters of that market will surely trigger intense scrutiny by the agencies."

Samir Sakpal, an industry research manager at Frost & Sullivan, says that in addition to having a dominant share of U.S. wireless subscribers, the "big three" carriers could also dominate proprietary spectrum in the United States and thus make it virtually impossible for any new competitor to enter the market.

"I do think the [AT&T/T-Mobile merger] would raise the barrier to entry too high," he says. "It will get increasingly difficult for new market participants to enter."

On the other hand, Sakpal does think industry consolidation has been on the whole good for many wireless subscribers, as it's allowed carriers to provide more coverage to more places and to help consumers avoid costly roaming charges. He thinks that AT&T's T-Mobile acquisition will work out especially well for customers of both carriers since AT&T and T-Mobile both already are using HSPA+ technology for their mobile broadband services and both are planning to launch LTE networks over the next two years.