A Silicon Valley start-up that sought permission to build a "free, family-friendly" wireless Internet service on a stretch of unused radio spectrum has been shot down by federal regulators. The Federal Communications Commission rejected a nearly 16-month-old petition by Menlo Park, Calif.-based M2Z Networks to receive an exclusive, 15-year license to build and operate such a network in the 2155MHz-to-2175MHz band, in return for depositing a portion of its revenues into the U.S. Treasury.