AT&T Inc. and Verizon Communications Inc. were on the defensive last week after accusations swirled they were throttling the quality of Netflix Inc. video on their wireless networks. , a leading proponent of open Internet rules, has been lowering the quality of its video for customers watching its service on AT&T The popular video service said Thursday that for more than five years it has limited its videos to most wireless carriers across the globe, including AT&T and Verizon, to "protect consumers from exceeding mobile data caps," which may discourage future viewing.