Our thirst for mobile data is only getting stronger as smartphones get faster and more powerful.This year, the average U.S. cellphone user consumed 1.2 GB of data per month, the New York Times reports, citing a study by mobile analyst Chetan Sharma. That's nearly double the 690 MB consumed by the average user a year ago.Not surprisingly, Sharma attributed the growth in data use to faster 4G LTE networks and more advanced smartphones, which can handle increasingly larger images and videos.More sophisticated apps with larger file sizes may also have played a role. Although Apple prevents users from downloading huge apps without a Wi-Fi connection, in September the company raised the mobile download size limit from 50 MB to 100 MB. Android devices don't have a size limit for app downloads over mobile broadband.For AT&T and Verizon Wireless, everything's going as planned.