Telecom heavyweights joined Facebook's Open Compute project on Wednesday, bringing more heft to the social media giant's crusade to bring low-cost data center gear to the masses and potentially jeopardizing Cisco's dominance in the carrier infrastructure space. U.S.-based AT&T and Verizon, German carrier Deutsche Telekom, British mobile network operator EE and South Korea's SK Telecom signed on to back Facebook's foundation for open-source data center design.