A data center critical for allowing uninsured Americans to buy health coverage under President Barack Obama's healthcare law went down on Sunday, the U.S. government said, in the latest problem for the "Obamacare'' rollout. Verizon's Terremark operates the data center behind a federal system for determining eligibility for government subsidies to buy insurance nationwide and hosts HealthCare.gov, the website that makes insurance available in 36 of the 50 states. The data center experienced a failure on Sunday that led it to lose network connectivity, Health and Human Services Department spokeswoman Joanne Peters said. The U.S. Centers for Medicare and Medicaid...