Mobile devices are set to surpass the traditional desktop PC as the most common way to access the Internet. With more users turning to their phones to send e-mail, downloading applications and watching videos why are U.S carriers still feeling the pinch?

According to a report from the Wall Street Journal, wireless carriers spend more to deliver the data-intensive requirements of smartphone applications like web surfing, video streaming and data downloading. The wireless industry spent $24.9 billion in 2010 to invest in infrastructure to support the incessant need for more data traffic.

Carriers have been saddled with rising capital costs while smartphone manufacturers like Apple Inc, companies using Google Inc.'s Android software and app makers walk away with the bulk of the profit from the burgeoning smartphone industry. Revenue from voice calls have been declining as the amount of wireless data consumed monthly have been rising. Even text messaging has been encroached upon by new applications like Apple's iMessage that allow users to communicate with each other without any texting charges. Carriers are now trying to catch up by charging for data usage but it won't be enough to cover the expenses as carriers buy more airwaves to support the deluge of data.

The trend is only getting worse. Wall Street Journal cited Nomura Securities analyst Michael McCormack who estimated that AT&T's profit margins will dip from 44 percent to 30 percent in the fourth quarter of this year. Even as more consumers buy iPhones from AT&T, the carrier has to pay Apple a subsidy of about $400 each time they sell an iPhone with a two-year contract.

So where does that leave carriers in the future? One scenario that can play out is that carriers will simply be data carriers, competing on price per bit. Carriers can make additional revenue by selling non- personally identifiable information about their subscribers to third-party vendors. The information will be sold to advertisers, publishers and businesses for a profit.