But fears have grown that some of them have been giving their data subscribers an early peek, through customised feeds that media groups have been allowed to install in the lockup room.

ECONOMIST: Financial data

The same process applies to unlimited data plan subscribers at 5GB of data use with the 4G LTE smartphone.

FORBES: AT&T's New Data Policy for Heavy Users

Verizon is also hoping shared-data plans convince subscribers to connect more devices to its network and pay more for service.

WSJ: Verizon Wireless Overhauls Wireless Plans