Internet advocacy group Public Knowledge has wireless broadband service providers in its sights and is urging the U.S. government to regulate operators' efforts to implement usage-based billing and cap broadband data consumption. In a fresh white paper, the group called for federal regulatory oversight of data capping practices by both wired and wireless service providers. The group also stated that service providers should be required to supply documentation regarding the number of users who exceed data caps and what they pay (in total and on average) in overage penalties. In a related action, Public Knowledge sent letters seeking detailed information on data cap practices and overage charges to four mobile operators and five fixed broadband operators--AT&T Mobility, Verizon Wireless, T-Mobile USA, Sprint Nextel, Verizon Communications, AT&T, Comcast, Time Warner Cable and Cox Cable. The advocacy group also joined with Free Press and others to deliver a letter to the U.S. Senate Commerce, Science and Transportation Committee, in which they asked the committee to investigate alleged harms that data caps have caused to consumers. See a summary of the conclusions and recommendations from Public Knowledge's white paper here.