Wireless substitution (using a mobile phone as a primary line, and not subscribing to wired phone service) is a big deal for the telecom industry. It will get bigger.
Philadelphia Inquirer: "[T]elecom industry analysts estimate that 3 percent to 5 percent of all wireless users are cord cutters, a figure that could increase to 10 percent in the next few years. And for the highly mobile 18- to 30-year-old demographic, some predict that half of all cell-phone users will have some period in their lives when they will get along without an old-fashioned phone. Already, probably 10 percent of them live without them, said Keith Mallinson, an analyst with the Yankee Group, a market research firm specializing in telecommunications."