"Skype's iPhone client was really the first shot across the bow of cellular carriers," he says. "As they build out higher speed data networks it becomes easier to do voice over data services."

This could spell trouble for carriers, Lazar explains, because they will inevitably lose revenue if users simply subscribe to flat-rate data plans and then use Skype exclusively for their voice services. Should Skype succeed in becoming a widely used VoIP technology that rides on top of carriers' data networks, Lazar thinks they have a few options to preserve their revenue streams: they can block Skype outright on their data services, they can implement their own metered data plans that charge per bit consumed or they can offer their own flat-rate VoIP service that is priced competitively with Skype's service.

Blocking Skype all together is unlikely, says Infonetics Research analyst Diane Myers, because companies such as Google and Apple have been putting pressure on carriers to not wall off their networks and to let their users access any application they wish.

"IPhone and Android platform are really breaking down barriers for traditional telecom companies," she says. "What they're interested in doing is the polar opposite of what telecom companies have been traditionally interested in."

And besides, Lazar notes, it would only take one smaller carrier such as T-Mobile offering to host Skype over its data network to foil the big incumbents' competitive advantage in keeping Skype off their own networks. This means that the telcos will at some point have to come up with their own IP-based voice services that will compete with Skype in offering lower-cost calls than traditional cellular networks.